crypto.md

# Crypto

<!--introduced_in=v0.3.6-->

> Stability: 2 - Stable

<!-- source_link=lib/crypto.js -->

The `crypto` module provides cryptographic functionality that includes a set of
wrappers for OpenSSL's hash, HMAC, cipher, decipher, sign, and verify functions.

```mjs
const { createHmac } = await import('crypto');

const secret = 'abcdefg';
const hash = createHmac('sha256', secret)
               .update('I love cupcakes')
               .digest('hex');
console.log(hash);
// Prints:
//   c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e
```

```cjs
const crypto = require('crypto');

const secret = 'abcdefg';
const hash = crypto.createHmac('sha256', secret)
                   .update('I love cupcakes')
                   .digest('hex');
console.log(hash);
// Prints:
//   c0fa1bc00531bd78ef38c628449c5102aeabd49b5dc3a2a516ea6ea959d6658e
```

## Determining if crypto support is unavailable

It is possible for Node.js to be built without including support for the
`crypto` module. In such cases, attempting to `import` from `crypto` or
calling `require('crypto')` will result in an error being thrown.

When using CommonJS, the error thrown can be caught using try/catch:

```cjs
let crypto;
try {
  crypto = require('crypto');
} catch (err) {
  console.log('crypto support is disabled!');
}
```

When using the lexical ESM `import` keyword, the error can only be
caught if a handler for `process.on('uncaughtException')` is registered
_before_ any attempt to load the module is made -- using, for instance,
a preload module.

When using ESM, if there is a chance that the code may be run on a build
of Node.js where crypto support is not enabled, consider using the
`import()` function instead of the lexical `import` keyword:

```mjs
let crypto;
try {
  crypto = await import('crypto');
} catch (err) {
  console.log('crypto support is disabled!');
}
```

## Class: `Certificate`

<!-- YAML
added: v0.11.8
-->

SPKAC is a Certificate Signing Request mechanism originally implemented by
Netscape and was specified formally as part of [HTML5's `keygen` element][].

`<keygen>` is deprecated since [HTML 5.2][] and new projects
should not use this element anymore.

The `crypto` module provides the `Certificate` class for working with SPKAC
data. The most common usage is handling output generated by the HTML5
`<keygen>` element. Node.js uses [OpenSSL's SPKAC implementation][] internally.

### Static method: `Certificate.exportChallenge(spkac[, encoding])`

<!-- YAML
added: v9.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The spkac argument can be an ArrayBuffer. Limited the size of
                 the spkac argument to a maximum of 2**31 - 1 bytes.
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {Buffer} The challenge component of the `spkac` data structure, which
  includes a public key and a challenge.

```mjs
const { Certificate } = await import('crypto');
const spkac = getSpkacSomehow();
const challenge = Certificate.exportChallenge(spkac);
console.log(challenge.toString('utf8'));
// Prints: the challenge as a UTF8 string
```

```cjs
const { Certificate } = require('crypto');
const spkac = getSpkacSomehow();
const challenge = Certificate.exportChallenge(spkac);
console.log(challenge.toString('utf8'));
// Prints: the challenge as a UTF8 string
```

### Static method: `Certificate.exportPublicKey(spkac[, encoding])`

<!-- YAML
added: v9.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The spkac argument can be an ArrayBuffer. Limited the size of
                 the spkac argument to a maximum of 2**31 - 1 bytes.
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {Buffer} The public key component of the `spkac` data structure,
  which includes a public key and a challenge.

```mjs
const { Certificate } = await import('crypto');
const spkac = getSpkacSomehow();
const publicKey = Certificate.exportPublicKey(spkac);
console.log(publicKey);
// Prints: the public key as <Buffer ...>
```

```cjs
const { Certificate } = require('crypto');
const spkac = getSpkacSomehow();
const publicKey = Certificate.exportPublicKey(spkac);
console.log(publicKey);
// Prints: the public key as <Buffer ...>
```

### Static method: `Certificate.verifySpkac(spkac[, encoding])`

<!-- YAML
added: v9.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The spkac argument can be an ArrayBuffer. Added encoding.
                 Limited the size of the spkac argument to a maximum of
                 2**31 - 1 bytes.
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {boolean} `true` if the given `spkac` data structure is valid,
  `false` otherwise.

```mjs
import { Buffer } from 'buffer';
const { Certificate } = await import('crypto');

const spkac = getSpkacSomehow();
console.log(Certificate.verifySpkac(Buffer.from(spkac)));
// Prints: true or false
```

```cjs
const { Certificate } = require('crypto');
const { Buffer } = require('buffer');

const spkac = getSpkacSomehow();
console.log(Certificate.verifySpkac(Buffer.from(spkac)));
// Prints: true or false
```

### Legacy API

> Stability: 0 - Deprecated

As a legacy interface, it is possible to create new instances of
the `crypto.Certificate` class as illustrated in the examples below.

#### `new crypto.Certificate()`

Instances of the `Certificate` class can be created using the `new` keyword
or by calling `crypto.Certificate()` as a function:

```mjs
const { Certificate } = await import('crypto');

const cert1 = new Certificate();
const cert2 = Certificate();
```

```cjs
const { Certificate } = require('crypto');

const cert1 = new Certificate();
const cert2 = Certificate();
```

#### `certificate.exportChallenge(spkac[, encoding])`

<!-- YAML
added: v0.11.8
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {Buffer} The challenge component of the `spkac` data structure, which
  includes a public key and a challenge.

```mjs
const { Certificate } = await import('crypto');
const cert = Certificate();
const spkac = getSpkacSomehow();
const challenge = cert.exportChallenge(spkac);
console.log(challenge.toString('utf8'));
// Prints: the challenge as a UTF8 string
```

```cjs
const { Certificate } = require('crypto');
const cert = Certificate();
const spkac = getSpkacSomehow();
const challenge = cert.exportChallenge(spkac);
console.log(challenge.toString('utf8'));
// Prints: the challenge as a UTF8 string
```

#### `certificate.exportPublicKey(spkac[, encoding])`

<!-- YAML
added: v0.11.8
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {Buffer} The public key component of the `spkac` data structure,
  which includes a public key and a challenge.

```mjs
const { Certificate } = await import('crypto');
const cert = Certificate();
const spkac = getSpkacSomehow();
const publicKey = cert.exportPublicKey(spkac);
console.log(publicKey);
// Prints: the public key as <Buffer ...>
```

```cjs
const { Certificate } = require('crypto');
const cert = Certificate();
const spkac = getSpkacSomehow();
const publicKey = cert.exportPublicKey(spkac);
console.log(publicKey);
// Prints: the public key as <Buffer ...>
```

#### `certificate.verifySpkac(spkac[, encoding])`

<!-- YAML
added: v0.11.8
-->

* `spkac` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `spkac` string.
* Returns: {boolean} `true` if the given `spkac` data structure is valid,
  `false` otherwise.

```mjs
import { Buffer } from 'buffer';
const { Certificate } = await import('crypto');

const cert = Certificate();
const spkac = getSpkacSomehow();
console.log(cert.verifySpkac(Buffer.from(spkac)));
// Prints: true or false
```

```cjs
const { Certificate } = require('crypto');
const { Buffer } = require('buffer');

const cert = Certificate();
const spkac = getSpkacSomehow();
console.log(cert.verifySpkac(Buffer.from(spkac)));
// Prints: true or false
```

## Class: `Cipher`

<!-- YAML
added: v0.1.94
-->

* Extends: {stream.Transform}

Instances of the `Cipher` class are used to encrypt data. The class can be
used in one of two ways:

* As a [stream][] that is both readable and writable, where plain unencrypted
  data is written to produce encrypted data on the readable side, or
* Using the [`cipher.update()`][] and [`cipher.final()`][] methods to produce
  the encrypted data.

The [`crypto.createCipher()`][] or [`crypto.createCipheriv()`][] methods are
used to create `Cipher` instances. `Cipher` objects are not to be created
directly using the `new` keyword.

Example: Using `Cipher` objects as streams:

```mjs
const {
  scrypt,
  randomFill,
  createCipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    // Once we have the key and iv, we can create and use the cipher...
    const cipher = createCipheriv(algorithm, key, iv);

    let encrypted = '';
    cipher.setEncoding('hex');

    cipher.on('data', (chunk) => encrypted += chunk);
    cipher.on('end', () => console.log(encrypted));

    cipher.write('some clear text data');
    cipher.end();
  });
});
```

```cjs
const {
  scrypt,
  randomFill,
  createCipheriv
} = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    // Once we have the key and iv, we can create and use the cipher...
    const cipher = createCipheriv(algorithm, key, iv);

    let encrypted = '';
    cipher.setEncoding('hex');

    cipher.on('data', (chunk) => encrypted += chunk);
    cipher.on('end', () => console.log(encrypted));

    cipher.write('some clear text data');
    cipher.end();
  });
});
```

Example: Using `Cipher` and piped streams:

```mjs
import {
  createReadStream,
  createWriteStream,
} from 'fs';

import {
  pipeline
} from 'stream';

const {
  scrypt,
  randomFill,
  createCipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    const cipher = createCipheriv(algorithm, key, iv);

    const input = createReadStream('test.js');
    const output = createWriteStream('test.enc');

    pipeline(input, cipher, output, (err) => {
      if (err) throw err;
    });
  });
});
```

```cjs
const {
  createReadStream,
  createWriteStream,
} = require('fs');

const {
  pipeline
} = require('stream');

const {
  scrypt,
  randomFill,
  createCipheriv,
} = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    const cipher = createCipheriv(algorithm, key, iv);

    const input = createReadStream('test.js');
    const output = createWriteStream('test.enc');

    pipeline(input, cipher, output, (err) => {
      if (err) throw err;
    });
  });
});
```

Example: Using the [`cipher.update()`][] and [`cipher.final()`][] methods:

```mjs
const {
  scrypt,
  randomFill,
  createCipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    const cipher = createCipheriv(algorithm, key, iv);

    let encrypted = cipher.update('some clear text data', 'utf8', 'hex');
    encrypted += cipher.final('hex');
    console.log(encrypted);
  });
});
```

```cjs
const {
  scrypt,
  randomFill,
  createCipheriv,
} = require('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';

// First, we'll generate the key. The key length is dependent on the algorithm.
// In this case for aes192, it is 24 bytes (192 bits).
scrypt(password, 'salt', 24, (err, key) => {
  if (err) throw err;
  // Then, we'll generate a random initialization vector
  randomFill(new Uint8Array(16), (err, iv) => {
    if (err) throw err;

    const cipher = createCipheriv(algorithm, key, iv);

    let encrypted = cipher.update('some clear text data', 'utf8', 'hex');
    encrypted += cipher.final('hex');
    console.log(encrypted);
  });
});
```

### `cipher.final([outputEncoding])`

<!-- YAML
added: v0.1.94
-->

* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string} Any remaining enciphered contents.
  If `outputEncoding` is specified, a string is
  returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned.

Once the `cipher.final()` method has been called, the `Cipher` object can no
longer be used to encrypt data. Attempts to call `cipher.final()` more than
once will result in an error being thrown.

### `cipher.getAuthTag()`

<!-- YAML
added: v1.0.0
-->

* Returns: {Buffer} When using an authenticated encryption mode (`GCM`, `CCM`
  and `OCB` are currently supported), the `cipher.getAuthTag()` method returns a
  [`Buffer`][] containing the _authentication tag_ that has been computed from
  the given data.

The `cipher.getAuthTag()` method should only be called after encryption has
been completed using the [`cipher.final()`][] method.

If the `authTagLength` option was set during the `cipher` instance's creation,
this function will return exactly `authTagLength` bytes.

### `cipher.setAAD(buffer[, options])`

<!-- YAML
added: v1.0.0
-->

* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `options` {Object} [`stream.transform` options][]
  * `plaintextLength` {number}
  * `encoding` {string} The string encoding to use when `buffer` is a string.
* Returns: {Cipher} for method chaining.

When using an authenticated encryption mode (`GCM`, `CCM` and `OCB` are
currently supported), the `cipher.setAAD()` method sets the value used for the
_additional authenticated data_ (AAD) input parameter.

The `plaintextLength` option is optional for `GCM` and `OCB`. When using `CCM`,
the `plaintextLength` option must be specified and its value must match the
length of the plaintext in bytes. See [CCM mode][].

The `cipher.setAAD()` method must be called before [`cipher.update()`][].

### `cipher.setAutoPadding([autoPadding])`

<!-- YAML
added: v0.7.1
-->

* `autoPadding` {boolean} **Default:** `true`
* Returns: {Cipher} for method chaining.

When using block encryption algorithms, the `Cipher` class will automatically
add padding to the input data to the appropriate block size. To disable the
default padding call `cipher.setAutoPadding(false)`.

When `autoPadding` is `false`, the length of the entire input data must be a
multiple of the cipher's block size or [`cipher.final()`][] will throw an error.
Disabling automatic padding is useful for non-standard padding, for instance
using `0x0` instead of PKCS padding.

The `cipher.setAutoPadding()` method must be called before
[`cipher.final()`][].

### `cipher.update(data[, inputEncoding][, outputEncoding])`

<!-- YAML
added: v0.1.94
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the data.
* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Updates the cipher with `data`. If the `inputEncoding` argument is given,
the `data`
argument is a string using the specified encoding. If the `inputEncoding`
argument is not given, `data` must be a [`Buffer`][], `TypedArray`, or
`DataView`. If `data` is a [`Buffer`][], `TypedArray`, or `DataView`, then
`inputEncoding` is ignored.

The `outputEncoding` specifies the output format of the enciphered
data. If the `outputEncoding`
is specified, a string using the specified encoding is returned. If no
`outputEncoding` is provided, a [`Buffer`][] is returned.

The `cipher.update()` method can be called multiple times with new data until
[`cipher.final()`][] is called. Calling `cipher.update()` after
[`cipher.final()`][] will result in an error being thrown.

## Class: `Decipher`

<!-- YAML
added: v0.1.94
-->

* Extends: {stream.Transform}

Instances of the `Decipher` class are used to decrypt data. The class can be
used in one of two ways:

* As a [stream][] that is both readable and writable, where plain encrypted
  data is written to produce unencrypted data on the readable side, or
* Using the [`decipher.update()`][] and [`decipher.final()`][] methods to
  produce the unencrypted data.

The [`crypto.createDecipher()`][] or [`crypto.createDecipheriv()`][] methods are
used to create `Decipher` instances. `Decipher` objects are not to be created
directly using the `new` keyword.

Example: Using `Decipher` objects as streams:

```mjs
import { Buffer } from 'buffer';
const {
  scryptSync,
  createDecipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Key length is dependent on the algorithm. In this case for aes192, it is
// 24 bytes (192 bits).
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

let decrypted = '';
decipher.on('readable', () => {
  while (null !== (chunk = decipher.read())) {
    decrypted += chunk.toString('utf8');
  }
});
decipher.on('end', () => {
  console.log(decrypted);
  // Prints: some clear text data
});

// Encrypted with same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
decipher.write(encrypted, 'hex');
decipher.end();
```

```cjs
const {
  scryptSync,
  createDecipheriv,
} = require('crypto');
const { Buffer } = require('buffer');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Key length is dependent on the algorithm. In this case for aes192, it is
// 24 bytes (192 bits).
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

let decrypted = '';
decipher.on('readable', () => {
  while (null !== (chunk = decipher.read())) {
    decrypted += chunk.toString('utf8');
  }
});
decipher.on('end', () => {
  console.log(decrypted);
  // Prints: some clear text data
});

// Encrypted with same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
decipher.write(encrypted, 'hex');
decipher.end();
```

Example: Using `Decipher` and piped streams:

```mjs
import {
  createReadStream,
  createWriteStream,
} from 'fs';
import { Buffer } from 'buffer';
const {
  scryptSync,
  createDecipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

const input = createReadStream('test.enc');
const output = createWriteStream('test.js');

input.pipe(decipher).pipe(output);
```

```cjs
const {
  createReadStream,
  createWriteStream,
} = require('fs');
const {
  scryptSync,
  createDecipheriv,
} = require('crypto');
const { Buffer } = require('buffer');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

const input = createReadStream('test.enc');
const output = createWriteStream('test.js');

input.pipe(decipher).pipe(output);
```

Example: Using the [`decipher.update()`][] and [`decipher.final()`][] methods:

```mjs
import { Buffer } from 'buffer';
const {
  scryptSync,
  createDecipheriv
} = await import('crypto');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

// Encrypted using same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
let decrypted = decipher.update(encrypted, 'hex', 'utf8');
decrypted += decipher.final('utf8');
console.log(decrypted);
// Prints: some clear text data
```

```cjs
const {
  scryptSync,
  createDecipheriv,
} = require('crypto');
const { Buffer } = require('buffer');

const algorithm = 'aes-192-cbc';
const password = 'Password used to generate key';
// Use the async `crypto.scrypt()` instead.
const key = scryptSync(password, 'salt', 24);
// The IV is usually passed along with the ciphertext.
const iv = Buffer.alloc(16, 0); // Initialization vector.

const decipher = createDecipheriv(algorithm, key, iv);

// Encrypted using same algorithm, key and iv.
const encrypted =
  'e5f79c5915c02171eec6b212d5520d44480993d7d622a7c4c2da32f6efda0ffa';
let decrypted = decipher.update(encrypted, 'hex', 'utf8');
decrypted += decipher.final('utf8');
console.log(decrypted);
// Prints: some clear text data
```

### `decipher.final([outputEncoding])`

<!-- YAML
added: v0.1.94
-->

* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string} Any remaining deciphered contents.
  If `outputEncoding` is specified, a string is
  returned. If an `outputEncoding` is not provided, a [`Buffer`][] is returned.

Once the `decipher.final()` method has been called, the `Decipher` object can
no longer be used to decrypt data. Attempts to call `decipher.final()` more
than once will result in an error being thrown.

### `decipher.setAAD(buffer[, options])`

<!-- YAML
added: v1.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The buffer argument can be a string or ArrayBuffer and is
                limited to no more than 2 ** 31 - 1 bytes.
  - version: v7.2.0
    pr-url: https://github.com/nodejs/node/pull/9398
    description: This method now returns a reference to `decipher`.
-->

* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `options` {Object} [`stream.transform` options][]
  * `plaintextLength` {number}
  * `encoding` {string} String encoding to use when `buffer` is a string.
* Returns: {Decipher} for method chaining.

When using an authenticated encryption mode (`GCM`, `CCM` and `OCB` are
currently supported), the `decipher.setAAD()` method sets the value used for the
_additional authenticated data_ (AAD) input parameter.

The `options` argument is optional for `GCM`. When using `CCM`, the
`plaintextLength` option must be specified and its value must match the length
of the ciphertext in bytes. See [CCM mode][].

The `decipher.setAAD()` method must be called before [`decipher.update()`][].

When passing a string as the `buffer`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

### `decipher.setAuthTag(buffer[, encoding])`

<!-- YAML
added: v1.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The buffer argument can be a string or ArrayBuffer and is
                limited to no more than 2 ** 31 - 1 bytes.
  - version: v11.0.0
    pr-url: https://github.com/nodejs/node/pull/17825
    description: This method now throws if the GCM tag length is invalid.
  - version: v7.2.0
    pr-url: https://github.com/nodejs/node/pull/9398
    description: This method now returns a reference to `decipher`.
-->

* `buffer` {string|Buffer|ArrayBuffer|TypedArray|DataView}
* `encoding` {string} String encoding to use when `buffer` is a string.
* Returns: {Decipher} for method chaining.

When using an authenticated encryption mode (`GCM`, `CCM` and `OCB` are
currently supported), the `decipher.setAuthTag()` method is used to pass in the
received _authentication tag_. If no tag is provided, or if the cipher text
has been tampered with, [`decipher.final()`][] will throw, indicating that the
cipher text should be discarded due to failed authentication. If the tag length
is invalid according to [NIST SP 800-38D][] or does not match the value of the
`authTagLength` option, `decipher.setAuthTag()` will throw an error.

The `decipher.setAuthTag()` method must be called before [`decipher.update()`][]
for `CCM` mode or before [`decipher.final()`][] for `GCM` and `OCB` modes.
`decipher.setAuthTag()` can only be called once.

When passing a string as the authentication tag, please consider
[caveats when using strings as inputs to cryptographic APIs][].

### `decipher.setAutoPadding([autoPadding])`

<!-- YAML
added: v0.7.1
-->

* `autoPadding` {boolean} **Default:** `true`
* Returns: {Decipher} for method chaining.

When data has been encrypted without standard block padding, calling
`decipher.setAutoPadding(false)` will disable automatic padding to prevent
[`decipher.final()`][] from checking for and removing padding.

Turning auto padding off will only work if the input data's length is a
multiple of the ciphers block size.

The `decipher.setAutoPadding()` method must be called before
[`decipher.final()`][].

### `decipher.update(data[, inputEncoding][, outputEncoding])`

<!-- YAML
added: v0.1.94
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `data` string.
* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Updates the decipher with `data`. If the `inputEncoding` argument is given,
the `data`
argument is a string using the specified encoding. If the `inputEncoding`
argument is not given, `data` must be a [`Buffer`][]. If `data` is a
[`Buffer`][] then `inputEncoding` is ignored.

The `outputEncoding` specifies the output format of the enciphered
data. If the `outputEncoding`
is specified, a string using the specified encoding is returned. If no
`outputEncoding` is provided, a [`Buffer`][] is returned.

The `decipher.update()` method can be called multiple times with new data until
[`decipher.final()`][] is called. Calling `decipher.update()` after
[`decipher.final()`][] will result in an error being thrown.

## Class: `DiffieHellman`

<!-- YAML
added: v0.5.0
-->

The `DiffieHellman` class is a utility for creating Diffie-Hellman key
exchanges.

Instances of the `DiffieHellman` class can be created using the
[`crypto.createDiffieHellman()`][] function.

```mjs
import assert from 'assert';

const {
  createDiffieHellman
} = await import('crypto');

// Generate Alice's keys...
const alice = createDiffieHellman(2048);
const aliceKey = alice.generateKeys();

// Generate Bob's keys...
const bob = createDiffieHellman(alice.getPrime(), alice.getGenerator());
const bobKey = bob.generateKeys();

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

// OK
assert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));
```

```cjs
const assert = require('assert');

const {
  createDiffieHellman,
} = require('crypto');

// Generate Alice's keys...
const alice = createDiffieHellman(2048);
const aliceKey = alice.generateKeys();

// Generate Bob's keys...
const bob = createDiffieHellman(alice.getPrime(), alice.getGenerator());
const bobKey = bob.generateKeys();

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

// OK
assert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));
```

### `diffieHellman.computeSecret(otherPublicKey[, inputEncoding][, outputEncoding])`

<!-- YAML
added: v0.5.0
-->

* `otherPublicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of an `otherPublicKey` string.
* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Computes the shared secret using `otherPublicKey` as the other
party's public key and returns the computed shared secret. The supplied
key is interpreted using the specified `inputEncoding`, and secret is
encoded using specified `outputEncoding`.
If the `inputEncoding` is not
provided, `otherPublicKey` is expected to be a [`Buffer`][],
`TypedArray`, or `DataView`.

If `outputEncoding` is given a string is returned; otherwise, a
[`Buffer`][] is returned.

### `diffieHellman.generateKeys([encoding])`

<!-- YAML
added: v0.5.0
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Generates private and public Diffie-Hellman key values, and returns
the public key in the specified `encoding`. This key should be
transferred to the other party.
If `encoding` is provided a string is returned; otherwise a
[`Buffer`][] is returned.

### `diffieHellman.getGenerator([encoding])`

<!-- YAML
added: v0.5.0
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Returns the Diffie-Hellman generator in the specified `encoding`.
If `encoding` is provided a string is
returned; otherwise a [`Buffer`][] is returned.

### `diffieHellman.getPrime([encoding])`

<!-- YAML
added: v0.5.0
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Returns the Diffie-Hellman prime in the specified `encoding`.
If `encoding` is provided a string is
returned; otherwise a [`Buffer`][] is returned.

### `diffieHellman.getPrivateKey([encoding])`

<!-- YAML
added: v0.5.0
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Returns the Diffie-Hellman private key in the specified `encoding`.
If `encoding` is provided a
string is returned; otherwise a [`Buffer`][] is returned.

### `diffieHellman.getPublicKey([encoding])`

<!-- YAML
added: v0.5.0
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Returns the Diffie-Hellman public key in the specified `encoding`.
If `encoding` is provided a
string is returned; otherwise a [`Buffer`][] is returned.

### `diffieHellman.setPrivateKey(privateKey[, encoding])`

<!-- YAML
added: v0.5.0
-->

* `privateKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `privateKey` string.

Sets the Diffie-Hellman private key. If the `encoding` argument is provided,
`privateKey` is expected
to be a string. If no `encoding` is provided, `privateKey` is expected
to be a [`Buffer`][], `TypedArray`, or `DataView`.

### `diffieHellman.setPublicKey(publicKey[, encoding])`

<!-- YAML
added: v0.5.0
-->

* `publicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `publicKey` string.

Sets the Diffie-Hellman public key. If the `encoding` argument is provided,
`publicKey` is expected
to be a string. If no `encoding` is provided, `publicKey` is expected
to be a [`Buffer`][], `TypedArray`, or `DataView`.

### `diffieHellman.verifyError`

<!-- YAML
added: v0.11.12
-->

A bit field containing any warnings and/or errors resulting from a check
performed during initialization of the `DiffieHellman` object.

The following values are valid for this property (as defined in `constants`
module):

* `DH_CHECK_P_NOT_SAFE_PRIME`
* `DH_CHECK_P_NOT_PRIME`
* `DH_UNABLE_TO_CHECK_GENERATOR`
* `DH_NOT_SUITABLE_GENERATOR`

## Class: `DiffieHellmanGroup`

<!-- YAML
added: v0.7.5
-->

The `DiffieHellmanGroup` class takes a well-known modp group as its argument.
It works the same as `DiffieHellman`, except that it does not allow changing
its keys after creation. In other words, it does not implement `setPublicKey()`
or `setPrivateKey()` methods.

```mjs
const { createDiffieHellmanGroup } = await import('crypto');
const dh = createDiffieHellmanGroup('modp1');
```

```cjs
const { createDiffieHellmanGroup } = require('crypto');
const dh = createDiffieHellmanGroup('modp1');
```

The name (e.g. `'modp1'`) is taken from [RFC 2412][] (modp1 and 2) and
[RFC 3526][]:

```console
$ perl -ne 'print "$1\n" if /"(modp\d+)"/' src/node_crypto_groups.h
modp1  #  768 bits
modp2  # 1024 bits
modp5  # 1536 bits
modp14 # 2048 bits
modp15 # etc.
modp16
modp17
modp18
```

## Class: `ECDH`

<!-- YAML
added: v0.11.14
-->

The `ECDH` class is a utility for creating Elliptic Curve Diffie-Hellman (ECDH)
key exchanges.

Instances of the `ECDH` class can be created using the
[`crypto.createECDH()`][] function.

```mjs
import assert from 'assert';

const {
  createECDH
} = await import('crypto');

// Generate Alice's keys...
const alice = createECDH('secp521r1');
const aliceKey = alice.generateKeys();

// Generate Bob's keys...
const bob = createECDH('secp521r1');
const bobKey = bob.generateKeys();

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

assert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));
// OK
```

```cjs
const assert = require('assert');

const {
  createECDH,
} = require('crypto');

// Generate Alice's keys...
const alice = createECDH('secp521r1');
const aliceKey = alice.generateKeys();

// Generate Bob's keys...
const bob = createECDH('secp521r1');
const bobKey = bob.generateKeys();

// Exchange and generate the secret...
const aliceSecret = alice.computeSecret(bobKey);
const bobSecret = bob.computeSecret(aliceKey);

assert.strictEqual(aliceSecret.toString('hex'), bobSecret.toString('hex'));
// OK
```

### Static method: `ECDH.convertKey(key, curve[, inputEncoding[, outputEncoding[, format]]])`

<!-- YAML
added: v10.0.0
-->

* `key` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `curve` {string}
* `inputEncoding` {string} The [encoding][] of the `key` string.
* `outputEncoding` {string} The [encoding][] of the return value.
* `format` {string} **Default:** `'uncompressed'`
* Returns: {Buffer | string}

Converts the EC Diffie-Hellman public key specified by `key` and `curve` to the
format specified by `format`. The `format` argument specifies point encoding
and can be `'compressed'`, `'uncompressed'` or `'hybrid'`. The supplied key is
interpreted using the specified `inputEncoding`, and the returned key is encoded
using the specified `outputEncoding`.

Use [`crypto.getCurves()`][] to obtain a list of available curve names.
On recent OpenSSL releases, `openssl ecparam -list_curves` will also display
the name and description of each available elliptic curve.

If `format` is not specified the point will be returned in `'uncompressed'`
format.

If the `inputEncoding` is not provided, `key` is expected to be a [`Buffer`][],
`TypedArray`, or `DataView`.

Example (uncompressing a key):

```mjs
const {
  createECDH,
  ECDH
} = await import('crypto');

const ecdh = createECDH('secp256k1');
ecdh.generateKeys();

const compressedKey = ecdh.getPublicKey('hex', 'compressed');

const uncompressedKey = ECDH.convertKey(compressedKey,
                                        'secp256k1',
                                        'hex',
                                        'hex',
                                        'uncompressed');

// The converted key and the uncompressed public key should be the same
console.log(uncompressedKey === ecdh.getPublicKey('hex'));
```

```cjs
const {
  createECDH,
  ECDH,
} = require('crypto');

const ecdh = createECDH('secp256k1');
ecdh.generateKeys();

const compressedKey = ecdh.getPublicKey('hex', 'compressed');

const uncompressedKey = ECDH.convertKey(compressedKey,
                                        'secp256k1',
                                        'hex',
                                        'hex',
                                        'uncompressed');

// The converted key and the uncompressed public key should be the same
console.log(uncompressedKey === ecdh.getPublicKey('hex'));
```

### `ecdh.computeSecret(otherPublicKey[, inputEncoding][, outputEncoding])`

<!-- YAML
added: v0.11.14
changes:
  - version: v10.0.0
    pr-url: https://github.com/nodejs/node/pull/16849
    description: Changed error format to better support invalid public key
                 error.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `otherPublicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `otherPublicKey` string.
* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Computes the shared secret using `otherPublicKey` as the other
party's public key and returns the computed shared secret. The supplied
key is interpreted using specified `inputEncoding`, and the returned secret
is encoded using the specified `outputEncoding`.
If the `inputEncoding` is not
provided, `otherPublicKey` is expected to be a [`Buffer`][], `TypedArray`, or
`DataView`.

If `outputEncoding` is given a string will be returned; otherwise a
[`Buffer`][] is returned.

`ecdh.computeSecret` will throw an
`ERR_CRYPTO_ECDH_INVALID_PUBLIC_KEY` error when `otherPublicKey`
lies outside of the elliptic curve. Since `otherPublicKey` is
usually supplied from a remote user over an insecure network,
be sure to handle this exception accordingly.

### `ecdh.generateKeys([encoding[, format]])`

<!-- YAML
added: v0.11.14
-->

* `encoding` {string} The [encoding][] of the return value.
* `format` {string} **Default:** `'uncompressed'`
* Returns: {Buffer | string}

Generates private and public EC Diffie-Hellman key values, and returns
the public key in the specified `format` and `encoding`. This key should be
transferred to the other party.

The `format` argument specifies point encoding and can be `'compressed'` or
`'uncompressed'`. If `format` is not specified, the point will be returned in
`'uncompressed'` format.

If `encoding` is provided a string is returned; otherwise a [`Buffer`][]
is returned.

### `ecdh.getPrivateKey([encoding])`

<!-- YAML
added: v0.11.14
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string} The EC Diffie-Hellman in the specified `encoding`.

If `encoding` is specified, a string is returned; otherwise a [`Buffer`][] is
returned.

### `ecdh.getPublicKey([encoding][, format])`

<!-- YAML
added: v0.11.14
-->

* `encoding` {string} The [encoding][] of the return value.
* `format` {string} **Default:** `'uncompressed'`
* Returns: {Buffer | string} The EC Diffie-Hellman public key in the specified
  `encoding` and `format`.

The `format` argument specifies point encoding and can be `'compressed'` or
`'uncompressed'`. If `format` is not specified the point will be returned in
`'uncompressed'` format.

If `encoding` is specified, a string is returned; otherwise a [`Buffer`][] is
returned.

### `ecdh.setPrivateKey(privateKey[, encoding])`

<!-- YAML
added: v0.11.14
-->

* `privateKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `privateKey` string.

Sets the EC Diffie-Hellman private key.
If `encoding` is provided, `privateKey` is expected
to be a string; otherwise `privateKey` is expected to be a [`Buffer`][],
`TypedArray`, or `DataView`.

If `privateKey` is not valid for the curve specified when the `ECDH` object was
created, an error is thrown. Upon setting the private key, the associated
public point (key) is also generated and set in the `ECDH` object.

### `ecdh.setPublicKey(publicKey[, encoding])`

<!-- YAML
added: v0.11.14
deprecated: v5.2.0
-->

> Stability: 0 - Deprecated

* `publicKey` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The [encoding][] of the `publicKey` string.

Sets the EC Diffie-Hellman public key.
If `encoding` is provided `publicKey` is expected to
be a string; otherwise a [`Buffer`][], `TypedArray`, or `DataView` is expected.

There is not normally a reason to call this method because `ECDH`
only requires a private key and the other party's public key to compute the
shared secret. Typically either [`ecdh.generateKeys()`][] or
[`ecdh.setPrivateKey()`][] will be called. The [`ecdh.setPrivateKey()`][] method
attempts to generate the public point/key associated with the private key being
set.

Example (obtaining a shared secret):

```mjs
const {
  createECDH,
  createHash
} = await import('crypto');

const alice = createECDH('secp256k1');
const bob = createECDH('secp256k1');

// This is a shortcut way of specifying one of Alice's previous private
// keys. It would be unwise to use such a predictable private key in a real
// application.
alice.setPrivateKey(
  createHash('sha256').update('alice', 'utf8').digest()
);

// Bob uses a newly generated cryptographically strong
// pseudorandom key pair
bob.generateKeys();

const aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

// aliceSecret and bobSecret should be the same shared secret value
console.log(aliceSecret === bobSecret);
```

```cjs
const {
  createECDH,
  createHash,
} = require('crypto');

const alice = createECDH('secp256k1');
const bob = createECDH('secp256k1');

// This is a shortcut way of specifying one of Alice's previous private
// keys. It would be unwise to use such a predictable private key in a real
// application.
alice.setPrivateKey(
  createHash('sha256').update('alice', 'utf8').digest()
);

// Bob uses a newly generated cryptographically strong
// pseudorandom key pair
bob.generateKeys();

const aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

// aliceSecret and bobSecret should be the same shared secret value
console.log(aliceSecret === bobSecret);
```

## Class: `Hash`

<!-- YAML
added: v0.1.92
-->

* Extends: {stream.Transform}

The `Hash` class is a utility for creating hash digests of data. It can be
used in one of two ways:

* As a [stream][] that is both readable and writable, where data is written
  to produce a computed hash digest on the readable side, or
* Using the [`hash.update()`][] and [`hash.digest()`][] methods to produce the
  computed hash.

The [`crypto.createHash()`][] method is used to create `Hash` instances. `Hash`
objects are not to be created directly using the `new` keyword.

Example: Using `Hash` objects as streams:

```mjs
const {
  createHash
} = await import('crypto');

const hash = createHash('sha256');

hash.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = hash.read();
  if (data) {
    console.log(data.toString('hex'));
    // Prints:
    //   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
  }
});

hash.write('some data to hash');
hash.end();
```

```cjs
const {
  createHash,
} = require('crypto');

const hash = createHash('sha256');

hash.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = hash.read();
  if (data) {
    console.log(data.toString('hex'));
    // Prints:
    //   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
  }
});

hash.write('some data to hash');
hash.end();
```

Example: Using `Hash` and piped streams:

```mjs
import { createReadStream } from 'fs';
import { stdout } from 'process';
const { createHash } = await import('crypto');

const hash = createHash('sha256');

const input = createReadStream('test.js');
input.pipe(hash).setEncoding('hex').pipe(stdout);
```

```cjs
const { createReadStream } = require('fs');
const { createHash } = require('crypto');
const { stdout } = require('process');

const hash = createHash('sha256');

const input = createReadStream('test.js');
input.pipe(hash).setEncoding('hex').pipe(stdout);
```

Example: Using the [`hash.update()`][] and [`hash.digest()`][] methods:

```mjs
const {
  createHash
} = await import('crypto');

const hash = createHash('sha256');

hash.update('some data to hash');
console.log(hash.digest('hex'));
// Prints:
//   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
```

```cjs
const {
  createHash,
} = require('crypto');

const hash = createHash('sha256');

hash.update('some data to hash');
console.log(hash.digest('hex'));
// Prints:
//   6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
```

### `hash.copy([options])`

<!-- YAML
added: v13.1.0
-->

* `options` {Object} [`stream.transform` options][]
* Returns: {Hash}

Creates a new `Hash` object that contains a deep copy of the internal state
of the current `Hash` object.

The optional `options` argument controls stream behavior. For XOF hash
functions such as `'shake256'`, the `outputLength` option can be used to
specify the desired output length in bytes.

An error is thrown when an attempt is made to copy the `Hash` object after
its [`hash.digest()`][] method has been called.

```mjs
// Calculate a rolling hash.
const {
  createHash
} = await import('crypto');

const hash = createHash('sha256');

hash.update('one');
console.log(hash.copy().digest('hex'));

hash.update('two');
console.log(hash.copy().digest('hex'));

hash.update('three');
console.log(hash.copy().digest('hex'));

// Etc.
```

```cjs
// Calculate a rolling hash.
const {
  createHash,
} = require('crypto');

const hash = createHash('sha256');

hash.update('one');
console.log(hash.copy().digest('hex'));

hash.update('two');
console.log(hash.copy().digest('hex'));

hash.update('three');
console.log(hash.copy().digest('hex'));

// Etc.
```

### `hash.digest([encoding])`

<!-- YAML
added: v0.1.92
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Calculates the digest of all of the data passed to be hashed (using the
[`hash.update()`][] method).
If `encoding` is provided a string will be returned; otherwise
a [`Buffer`][] is returned.

The `Hash` object can not be used again after `hash.digest()` method has been
called. Multiple calls will cause an error to be thrown.

### `hash.update(data[, inputEncoding])`

<!-- YAML
added: v0.1.92
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `data` string.

Updates the hash content with the given `data`, the encoding of which
is given in `inputEncoding`.
If `encoding` is not provided, and the `data` is a string, an
encoding of `'utf8'` is enforced. If `data` is a [`Buffer`][], `TypedArray`, or
`DataView`, then `inputEncoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: `Hmac`

<!-- YAML
added: v0.1.94
-->

* Extends: {stream.Transform}

The `Hmac` class is a utility for creating cryptographic HMAC digests. It can
be used in one of two ways:

* As a [stream][] that is both readable and writable, where data is written
  to produce a computed HMAC digest on the readable side, or
* Using the [`hmac.update()`][] and [`hmac.digest()`][] methods to produce the
  computed HMAC digest.

The [`crypto.createHmac()`][] method is used to create `Hmac` instances. `Hmac`
objects are not to be created directly using the `new` keyword.

Example: Using `Hmac` objects as streams:

```mjs
const {
  createHmac
} = await import('crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = hmac.read();
  if (data) {
    console.log(data.toString('hex'));
    // Prints:
    //   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
  }
});

hmac.write('some data to hash');
hmac.end();
```

```cjs
const {
  createHmac,
} = require('crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = hmac.read();
  if (data) {
    console.log(data.toString('hex'));
    // Prints:
    //   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
  }
});

hmac.write('some data to hash');
hmac.end();
```

Example: Using `Hmac` and piped streams:

```mjs
import { createReadStream } from 'fs';
import { stdout } from 'process';
const {
  createHmac
} = await import('crypto');

const hmac = createHmac('sha256', 'a secret');

const input = createReadStream('test.js');
input.pipe(hmac).pipe(stdout);
```

```cjs
const {
  createReadStream,
} = require('fs');
const {
  createHmac,
} = require('crypto');
const { stdout } = require('process');

const hmac = createHmac('sha256', 'a secret');

const input = createReadStream('test.js');
input.pipe(hmac).pipe(stdout);
```

Example: Using the [`hmac.update()`][] and [`hmac.digest()`][] methods:

```mjs
const {
  createHmac
} = await import('crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.update('some data to hash');
console.log(hmac.digest('hex'));
// Prints:
//   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
```

```cjs
const {
  createHmac,
} = require('crypto');

const hmac = createHmac('sha256', 'a secret');

hmac.update('some data to hash');
console.log(hmac.digest('hex'));
// Prints:
//   7fd04df92f636fd450bc841c9418e5825c17f33ad9c87c518115a45971f7f77e
```

### `hmac.digest([encoding])`

<!-- YAML
added: v0.1.94
-->

* `encoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

Calculates the HMAC digest of all of the data passed using [`hmac.update()`][].
If `encoding` is
provided a string is returned; otherwise a [`Buffer`][] is returned;

The `Hmac` object can not be used again after `hmac.digest()` has been
called. Multiple calls to `hmac.digest()` will result in an error being thrown.

### `hmac.update(data[, inputEncoding])`

<!-- YAML
added: v0.1.94
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `data` string.

Updates the `Hmac` content with the given `data`, the encoding of which
is given in `inputEncoding`.
If `encoding` is not provided, and the `data` is a string, an
encoding of `'utf8'` is enforced. If `data` is a [`Buffer`][], `TypedArray`, or
`DataView`, then `inputEncoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: `KeyObject`

<!-- YAML
added: v11.6.0
changes:
  - version:
    - v14.5.0
    - v12.19.0
    pr-url: https://github.com/nodejs/node/pull/33360
    description: Instances of this class can now be passed to worker threads
                 using `postMessage`.
  - version: v11.13.0
    pr-url: https://github.com/nodejs/node/pull/26438
    description: This class is now exported.
-->

Node.js uses a `KeyObject` class to represent a symmetric or asymmetric key,
and each kind of key exposes different functions. The
[`crypto.createSecretKey()`][], [`crypto.createPublicKey()`][] and
[`crypto.createPrivateKey()`][] methods are used to create `KeyObject`
instances. `KeyObject` objects are not to be created directly using the `new`
keyword.

Most applications should consider using the new `KeyObject` API instead of
passing keys as strings or `Buffer`s due to improved security features.

`KeyObject` instances can be passed to other threads via [`postMessage()`][].
The receiver obtains a cloned `KeyObject`, and the `KeyObject` does not need to
be listed in the `transferList` argument.

### Static method: `KeyObject.from(key)`

<!-- YAML
added: v15.0.0
-->

* `key` {CryptoKey}
* Returns: {KeyObject}

Example: Converting a `CryptoKey` instance to a `KeyObject`:

```mjs
const { webcrypto, KeyObject } = await import('crypto');
const { subtle } = webcrypto;

const key = await subtle.generateKey({
  name: 'HMAC',
  hash: 'SHA-256',
  length: 256
}, true, ['sign', 'verify']);

const keyObject = KeyObject.from(key);
console.log(keyObject.symmetricKeySize);
// Prints: 32 (symmetric key size in bytes)
```

```cjs
const {
  webcrypto: {
    subtle,
  },
  KeyObject,
} = require('crypto');

(async function() {
  const key = await subtle.generateKey({
    name: 'HMAC',
    hash: 'SHA-256',
    length: 256
  }, true, ['sign', 'verify']);

  const keyObject = KeyObject.from(key);
  console.log(keyObject.symmetricKeySize);
  // Prints: 32 (symmetric key size in bytes)
})();
```

### `keyObject.asymmetricKeyDetails`

<!-- YAML
added: v15.7.0
changes:
  - version: v16.9.0
    pr-url: https://github.com/nodejs/node/pull/39851
    description: Expose `RSASSA-PSS-params` sequence parameters
                 for RSA-PSS keys.
-->

* {Object}
  * `modulusLength`: {number} Key size in bits (RSA, DSA).
  * `publicExponent`: {bigint} Public exponent (RSA).
  * `hashAlgorithm`: {string} Name of the message digest (RSA-PSS).
  * `mgf1HashAlgorithm`: {string} Name of the message digest used by
    MGF1 (RSA-PSS).
  * `saltLength`: {number} Minimal salt length in bytes (RSA-PSS).
  * `divisorLength`: {number} Size of `q` in bits (DSA).
  * `namedCurve`: {string} Name of the curve (EC).

This property exists only on asymmetric keys. Depending on the type of the key,
this object contains information about the key. None of the information obtained
through this property can be used to uniquely identify a key or to compromise
the security of the key.

For RSA-PSS keys, if the key material contains a `RSASSA-PSS-params` sequence,
the `hashAlgorithm`, `mgf1HashAlgorithm`, and `saltLength` properties will be
set.

Other key details might be exposed via this API using additional attributes.

### `keyObject.asymmetricKeyType`

<!-- YAML
added: v11.6.0
changes:
  - version:
     - v13.9.0
     - v12.17.0
    pr-url: https://github.com/nodejs/node/pull/31178
    description: Added support for `'dh'`.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26960
    description: Added support for `'rsa-pss'`.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26786
    description: This property now returns `undefined` for KeyObject
                 instances of unrecognized type instead of aborting.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26774
    description: Added support for `'x25519'` and `'x448'`.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26319
    description: Added support for `'ed25519'` and `'ed448'`.
-->

* {string}

For asymmetric keys, this property represents the type of the key. Supported key
types are:

* `'rsa'` (OID 1.2.840.113549.1.1.1)
* `'rsa-pss'` (OID 1.2.840.113549.1.1.10)
* `'dsa'` (OID 1.2.840.10040.4.1)
* `'ec'` (OID 1.2.840.10045.2.1)
* `'x25519'` (OID 1.3.101.110)
* `'x448'` (OID 1.3.101.111)
* `'ed25519'` (OID 1.3.101.112)
* `'ed448'` (OID 1.3.101.113)
* `'dh'` (OID 1.2.840.113549.1.3.1)

This property is `undefined` for unrecognized `KeyObject` types and symmetric
keys.

### `keyObject.export([options])`

<!-- YAML
added: v11.6.0
changes:
  - version: v15.9.0
    pr-url: https://github.com/nodejs/node/pull/37081
    description: Added support for `'jwk'` format.
-->

* `options`: {Object}
* Returns: {string | Buffer | Object}

For symmetric keys, the following encoding options can be used:

* `format`: {string} Must be `'buffer'` (default) or `'jwk'`.

For public keys, the following encoding options can be used:

* `type`: {string} Must be one of `'pkcs1'` (RSA only) or `'spki'`.
* `format`: {string} Must be `'pem'`, `'der'`, or `'jwk'`.

For private keys, the following encoding options can be used:

* `type`: {string} Must be one of `'pkcs1'` (RSA only), `'pkcs8'` or
  `'sec1'` (EC only).
* `format`: {string} Must be `'pem'`, `'der'`, or `'jwk'`.
* `cipher`: {string} If specified, the private key will be encrypted with
  the given `cipher` and `passphrase` using PKCS#5 v2.0 password based
  encryption.
* `passphrase`: {string | Buffer} The passphrase to use for encryption, see
  `cipher`.

The result type depends on the selected encoding format, when PEM the
result is a string, when DER it will be a buffer containing the data
encoded as DER, when [JWK][] it will be an object.

When [JWK][] encoding format was selected, all other encoding options are
ignored.

PKCS#1, SEC1, and PKCS#8 type keys can be encrypted by using a combination of
the `cipher` and `format` options. The PKCS#8 `type` can be used with any
`format` to encrypt any key algorithm (RSA, EC, or DH) by specifying a
`cipher`. PKCS#1 and SEC1 can only be encrypted by specifying a `cipher`
when the PEM `format` is used. For maximum compatibility, use PKCS#8 for
encrypted private keys. Since PKCS#8 defines its own
encryption mechanism, PEM-level encryption is not supported when encrypting
a PKCS#8 key. See [RFC 5208][] for PKCS#8 encryption and [RFC 1421][] for
PKCS#1 and SEC1 encryption.

### `keyObject.symmetricKeySize`

<!-- YAML
added: v11.6.0
-->

* {number}

For secret keys, this property represents the size of the key in bytes. This
property is `undefined` for asymmetric keys.

### `keyObject.type`

<!-- YAML
added: v11.6.0
-->

* {string}

Depending on the type of this `KeyObject`, this property is either
`'secret'` for secret (symmetric) keys, `'public'` for public (asymmetric) keys
or `'private'` for private (asymmetric) keys.

## Class: `Sign`

<!-- YAML
added: v0.1.92
-->

* Extends: {stream.Writable}

The `Sign` class is a utility for generating signatures. It can be used in one
of two ways:

* As a writable [stream][], where data to be signed is written and the
  [`sign.sign()`][] method is used to generate and return the signature, or
* Using the [`sign.update()`][] and [`sign.sign()`][] methods to produce the
  signature.

The [`crypto.createSign()`][] method is used to create `Sign` instances. The
argument is the string name of the hash function to use. `Sign` objects are not
to be created directly using the `new` keyword.

Example: Using `Sign` and [`Verify`][] objects as streams:

```mjs
const {
  generateKeyPairSync,
  createSign,
  createVerify
} = await import('crypto');

const { privateKey, publicKey } = generateKeyPairSync('ec', {
  namedCurve: 'sect239k1'
});

const sign = createSign('SHA256');
sign.write('some data to sign');
sign.end();
const signature = sign.sign(privateKey, 'hex');

const verify = createVerify('SHA256');
verify.write('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature, 'hex'));
// Prints: true
```

```cjs
const {
  generateKeyPairSync,
  createSign,
  createVerify,
} = require('crypto');

const { privateKey, publicKey } = generateKeyPairSync('ec', {
  namedCurve: 'sect239k1'
});

const sign = createSign('SHA256');
sign.write('some data to sign');
sign.end();
const signature = sign.sign(privateKey, 'hex');

const verify = createVerify('SHA256');
verify.write('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature, 'hex'));
// Prints: true
```

Example: Using the [`sign.update()`][] and [`verify.update()`][] methods:

```mjs
const {
  generateKeyPairSync,
  createSign,
  createVerify
} = await import('crypto');

const { privateKey, publicKey } = generateKeyPairSync('rsa', {
  modulusLength: 2048,
});

const sign = createSign('SHA256');
sign.update('some data to sign');
sign.end();
const signature = sign.sign(privateKey);

const verify = createVerify('SHA256');
verify.update('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature));
// Prints: true
```

```cjs
const {
  generateKeyPairSync,
  createSign,
  createVerify,
} = require('crypto');

const { privateKey, publicKey } = generateKeyPairSync('rsa', {
  modulusLength: 2048,
});

const sign = createSign('SHA256');
sign.update('some data to sign');
sign.end();
const signature = sign.sign(privateKey);

const verify = createVerify('SHA256');
verify.update('some data to sign');
verify.end();
console.log(verify.verify(publicKey, signature));
// Prints: true
```

### `sign.sign(privateKey[, outputEncoding])`

<!-- YAML
added: v0.1.92
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The privateKey can also be an ArrayBuffer and CryptoKey.
  - version:
     - v13.2.0
     - v12.16.0
    pr-url: https://github.com/nodejs/node/pull/29292
    description: This function now supports IEEE-P1363 DSA and ECDSA signatures.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26960
    description: This function now supports RSA-PSS keys.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: This function now supports key objects.
  - version: v8.0.0
    pr-url: https://github.com/nodejs/node/pull/11705
    description: Support for RSASSA-PSS and additional options was added.
-->

<!--lint disable maximum-line-length remark-lint-->

* `privateKey` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `dsaEncoding` {string}
  * `padding` {integer}
  * `saltLength` {integer}
* `outputEncoding` {string} The [encoding][] of the return value.
* Returns: {Buffer | string}

<!--lint enable maximum-line-length remark-lint-->

Calculates the signature on all the data passed through using either
[`sign.update()`][] or [`sign.write()`][stream-writable-write].

If `privateKey` is not a [`KeyObject`][], this function behaves as if
`privateKey` had been passed to [`crypto.createPrivateKey()`][]. If it is an
object, the following additional properties can be passed:

* `dsaEncoding` {string} For DSA and ECDSA, this option specifies the
  format of the generated signature. It can be one of the following:
  * `'der'` (default): DER-encoded ASN.1 signature structure encoding `(r, s)`.
  * `'ieee-p1363'`: Signature format `r || s` as proposed in IEEE-P1363.
* `padding` {integer} Optional padding value for RSA, one of the following:

  * `crypto.constants.RSA_PKCS1_PADDING` (default)
  * `crypto.constants.RSA_PKCS1_PSS_PADDING`

  `RSA_PKCS1_PSS_PADDING` will use MGF1 with the same hash function
  used to sign the message as specified in section 3.1 of [RFC 4055][], unless
  an MGF1 hash function has been specified as part of the key in compliance with
  section 3.3 of [RFC 4055][].
* `saltLength` {integer} Salt length for when padding is
  `RSA_PKCS1_PSS_PADDING`. The special value
  `crypto.constants.RSA_PSS_SALTLEN_DIGEST` sets the salt length to the digest
  size, `crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN` (default) sets it to the
  maximum permissible value.

If `outputEncoding` is provided a string is returned; otherwise a [`Buffer`][]
is returned.

The `Sign` object can not be again used after `sign.sign()` method has been
called. Multiple calls to `sign.sign()` will result in an error being thrown.

### `sign.update(data[, inputEncoding])`

<!-- YAML
added: v0.1.92
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `data` string.

Updates the `Sign` content with the given `data`, the encoding of which
is given in `inputEncoding`.
If `encoding` is not provided, and the `data` is a string, an
encoding of `'utf8'` is enforced. If `data` is a [`Buffer`][], `TypedArray`, or
`DataView`, then `inputEncoding` is ignored.

This can be called many times with new data as it is streamed.

## Class: `Verify`

<!-- YAML
added: v0.1.92
-->

* Extends: {stream.Writable}

The `Verify` class is a utility for verifying signatures. It can be used in one
of two ways:

* As a writable [stream][] where written data is used to validate against the
  supplied signature, or
* Using the [`verify.update()`][] and [`verify.verify()`][] methods to verify
  the signature.

The [`crypto.createVerify()`][] method is used to create `Verify` instances.
`Verify` objects are not to be created directly using the `new` keyword.

See [`Sign`][] for examples.

### `verify.update(data[, inputEncoding])`

<!-- YAML
added: v0.1.92
changes:
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default `inputEncoding` changed from `binary` to `utf8`.
-->

* `data` {string|Buffer|TypedArray|DataView}
* `inputEncoding` {string} The [encoding][] of the `data` string.

Updates the `Verify` content with the given `data`, the encoding of which
is given in `inputEncoding`.
If `inputEncoding` is not provided, and the `data` is a string, an
encoding of `'utf8'` is enforced. If `data` is a [`Buffer`][], `TypedArray`, or
`DataView`, then `inputEncoding` is ignored.

This can be called many times with new data as it is streamed.

### `verify.verify(object, signature[, signatureEncoding])`

<!-- YAML
added: v0.1.92
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The object can also be an ArrayBuffer and CryptoKey.
  - version:
     - v13.2.0
     - v12.16.0
    pr-url: https://github.com/nodejs/node/pull/29292
    description: This function now supports IEEE-P1363 DSA and ECDSA signatures.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26960
    description: This function now supports RSA-PSS keys.
  - version: v11.7.0
    pr-url: https://github.com/nodejs/node/pull/25217
    description: The key can now be a private key.
  - version: v8.0.0
    pr-url: https://github.com/nodejs/node/pull/11705
    description: Support for RSASSA-PSS and additional options was added.
-->

<!--lint disable maximum-line-length remark-lint-->

* `object` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `dsaEncoding` {string}
  * `padding` {integer}
  * `saltLength` {integer}
* `signature` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `signatureEncoding` {string} The [encoding][] of the `signature` string.
* Returns: {boolean} `true` or `false` depending on the validity of the
  signature for the data and public key.

<!--lint enable maximum-line-length remark-lint-->

Verifies the provided data using the given `object` and `signature`.

If `object` is not a [`KeyObject`][], this function behaves as if
`object` had been passed to [`crypto.createPublicKey()`][]. If it is an
object, the following additional properties can be passed:

* `dsaEncoding` {string} For DSA and ECDSA, this option specifies the
  format of the signature. It can be one of the following:
  * `'der'` (default): DER-encoded ASN.1 signature structure encoding `(r, s)`.
  * `'ieee-p1363'`: Signature format `r || s` as proposed in IEEE-P1363.
* `padding` {integer} Optional padding value for RSA, one of the following:

  * `crypto.constants.RSA_PKCS1_PADDING` (default)
  * `crypto.constants.RSA_PKCS1_PSS_PADDING`

  `RSA_PKCS1_PSS_PADDING` will use MGF1 with the same hash function
  used to verify the message as specified in section 3.1 of [RFC 4055][], unless
  an MGF1 hash function has been specified as part of the key in compliance with
  section 3.3 of [RFC 4055][].
* `saltLength` {integer} Salt length for when padding is
  `RSA_PKCS1_PSS_PADDING`. The special value
  `crypto.constants.RSA_PSS_SALTLEN_DIGEST` sets the salt length to the digest
  size, `crypto.constants.RSA_PSS_SALTLEN_AUTO` (default) causes it to be
  determined automatically.

The `signature` argument is the previously calculated signature for the data, in
the `signatureEncoding`.
If a `signatureEncoding` is specified, the `signature` is expected to be a
string; otherwise `signature` is expected to be a [`Buffer`][],
`TypedArray`, or `DataView`.

The `verify` object can not be used again after `verify.verify()` has been
called. Multiple calls to `verify.verify()` will result in an error being
thrown.

Because public keys can be derived from private keys, a private key may
be passed instead of a public key.

## Class: `X509Certificate`

<!-- YAML
added: v15.6.0
-->

Encapsulates an X509 certificate and provides read-only access to
its information.

```mjs
const { X509Certificate } = await import('crypto');

const x509 = new X509Certificate('{... pem encoded cert ...}');

console.log(x509.subject);
```

```cjs
const { X509Certificate } = require('crypto');

const x509 = new X509Certificate('{... pem encoded cert ...}');

console.log(x509.subject);
```

### `new X509Certificate(buffer)`

<!-- YAML
added: v15.6.0
-->

* `buffer` {string|TypedArray|Buffer|DataView} A PEM or DER encoded
  X509 Certificate.

### `x509.ca`

<!-- YAML
added: v15.6.0
-->

* Type: {boolean} Will be `true` if this is a Certificate Authority (CA)
  certificate.

### `x509.checkEmail(email[, options])`

<!-- YAML
added: v15.6.0
changes:
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41600
    description: The subject option now defaults to `'default'`.
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41599
    description: The `wildcards`, `partialWildcards`, `multiLabelWildcards`, and
                 `singleLabelSubdomains` options have been removed since they
                 had no effect.
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41569
    description: The subject option can now be set to `'default'`.
-->

* `email` {string}
* `options` {Object}
  * `subject` {string} `'default'`, `'always'`, or `'never'`.
    **Default:** `'default'`.
* Returns: {string|undefined} Returns `email` if the certificate matches,
  `undefined` if it does not.

Checks whether the certificate matches the given email address.

If the `'subject'` option is undefined or set to `'default'`, the certificate
subject is only considered if the subject alternative name extension either does
not exist or does not contain any email addresses.

If the `'subject'` option is set to `'always'` and if the subject alternative
name extension either does not exist or does not contain a matching email
address, the certificate subject is considered.

If the `'subject'` option is set to `'never'`, the certificate subject is never
considered, even if the certificate contains no subject alternative names.

### `x509.checkHost(name[, options])`

<!-- YAML
added: v15.6.0
changes:
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41600
    description: The subject option now defaults to `'default'`.
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41569
    description: The subject option can now be set to `'default'`.
-->

* `name` {string}
* `options` {Object}
  * `subject` {string} `'default'`, `'always'`, or `'never'`.
    **Default:** `'default'`.
  * `wildcards` {boolean} **Default:** `true`.
  * `partialWildcards` {boolean} **Default:** `true`.
  * `multiLabelWildcards` {boolean} **Default:** `false`.
  * `singleLabelSubdomains` {boolean} **Default:** `false`.
* Returns: {string|undefined} Returns a subject name that matches `name`,
  or `undefined` if no subject name matches `name`.

Checks whether the certificate matches the given host name.

If the certificate matches the given host name, the matching subject name is
returned. The returned name might be an exact match (e.g., `foo.example.com`)
or it might contain wildcards (e.g., `*.example.com`). Because host name
comparisons are case-insensitive, the returned subject name might also differ
from the given `name` in capitalization.

If the `'subject'` option is undefined or set to `'default'`, the certificate
subject is only considered if the subject alternative name extension either does
not exist or does not contain any DNS names. This behavior is consistent with
[RFC 2818][] ("HTTP Over TLS").

If the `'subject'` option is set to `'always'` and if the subject alternative
name extension either does not exist or does not contain a matching DNS name,
the certificate subject is considered.

If the `'subject'` option is set to `'never'`, the certificate subject is never
considered, even if the certificate contains no subject alternative names.

### `x509.checkIP(ip)`

<!-- YAML
added: v15.6.0
changes:
  - version: REPLACEME
    pr-url: https://github.com/nodejs/node/pull/41571
    description: The `options` argument has been removed since it had no effect.
-->

* `ip` {string}
* Returns: {string|undefined} Returns `ip` if the certificate matches,
  `undefined` if it does not.

Checks whether the certificate matches the given IP address (IPv4 or IPv6).

Only [RFC 5280][] `iPAddress` subject alternative names are considered, and they
must match the given `ip` address exactly. Other subject alternative names as
well as the subject field of the certificate are ignored.

### `x509.checkIssued(otherCert)`

<!-- YAML
added: v15.6.0
-->

* `otherCert` {X509Certificate}
* Returns: {boolean}

Checks whether this certificate was issued by the given `otherCert`.

### `x509.checkPrivateKey(privateKey)`

<!-- YAML
added: v15.6.0
-->

* `privateKey` {KeyObject} A private key.
* Returns: {boolean}

Checks whether the public key for this certificate is consistent with
the given private key.

### `x509.fingerprint`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The SHA-1 fingerprint of this certificate.

### `x509.fingerprint256`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The SHA-256 fingerprint of this certificate.

### `x509.fingerprint512`

<!-- YAML
added: v17.2.0
-->

* Type: {string}

The SHA-512 fingerprint of this certificate.

### `x509.infoAccess`

<!-- YAML
added: v15.6.0
changes:
  - version:
      - v17.3.1
      - v16.13.2
    pr-url: https://github.com/nodejs-private/node-private/pull/300
    description: Parts of this string may be encoded as JSON string literals
                 in response to CVE-2021-44532.
-->

* Type: {string}

A textual representation of the certificate's authority information access
extension.

This is a line feed separated list of access descriptions. Each line begins with
the access method and the kind of the access location, followed by a colon and
the value associated with the access location.

After the prefix denoting the access method and the kind of the access location,
the remainder of each line might be enclosed in quotes to indicate that the
value is a JSON string literal. For backward compatibility, Node.js only uses
JSON string literals within this property when necessary to avoid ambiguity.
Third-party code should be prepared to handle both possible entry formats.

### `x509.issuer`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The issuer identification included in this certificate.

### `x509.issuerCertificate`

<!-- YAML
added: v15.9.0
-->

* Type: {X509Certificate}

The issuer certificate or `undefined` if the issuer certificate is not
available.

### `x509.keyUsage`

<!-- YAML
added: v15.6.0
-->

* Type: {string\[]}

An array detailing the key usages for this certificate.

### `x509.publicKey`

<!-- YAML
added: v15.6.0
-->

* Type: {KeyObject}

The public key {KeyObject} for this certificate.

### `x509.raw`

<!-- YAML
added: v15.6.0
-->

* Type: {Buffer}

A `Buffer` containing the DER encoding of this certificate.

### `x509.serialNumber`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The serial number of this certificate.

### `x509.subject`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The complete subject of this certificate.

### `x509.subjectAltName`

<!-- YAML
added: v15.6.0
changes:
  - version:
      - v17.3.1
      - v16.13.2
    pr-url: https://github.com/nodejs-private/node-private/pull/300
    description: Parts of this string may be encoded as JSON string literals
                 in response to CVE-2021-44532.
-->

* Type: {string}

The subject alternative name specified for this certificate.

This is a comma-separated list of subject alternative names. Each entry begins
with a string identifying the kind of the subject alternative name followed by
a colon and the value associated with the entry.

Earlier versions of Node.js incorrectly assumed that it is safe to split this
property at the two-character sequence `', '` (see [CVE-2021-44532][]). However,
both malicious and legitimate certificates can contain subject alternative names
that include this sequence when represented as a string.

After the prefix denoting the type of the entry, the remainder of each entry
might be enclosed in quotes to indicate that the value is a JSON string literal.
For backward compatibility, Node.js only uses JSON string literals within this
property when necessary to avoid ambiguity. Third-party code should be prepared
to handle both possible entry formats.

### `x509.toJSON()`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

There is no standard JSON encoding for X509 certificates. The
`toJSON()` method returns a string containing the PEM encoded
certificate.

### `x509.toLegacyObject()`

<!-- YAML
added: v15.6.0
-->

* Type: {Object}

Returns information about this certificate using the legacy
[certificate object][] encoding.

### `x509.toString()`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

Returns the PEM-encoded certificate.

### `x509.validFrom`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The date/time from which this certificate is considered valid.

### `x509.validTo`

<!-- YAML
added: v15.6.0
-->

* Type: {string}

The date/time until which this certificate is considered valid.

### `x509.verify(publicKey)`

<!-- YAML
added: v15.6.0
-->

* `publicKey` {KeyObject} A public key.
* Returns: {boolean}

Verifies that this certificate was signed by the given public key.
Does not perform any other validation checks on the certificate.

## `crypto` module methods and properties

### `crypto.constants`

<!-- YAML
added: v6.3.0
-->

* Returns: {Object} An object containing commonly used constants for crypto and
  security related operations. The specific constants currently defined are
  described in [Crypto constants][].

### `crypto.DEFAULT_ENCODING`

<!-- YAML
added: v0.9.3
deprecated: v10.0.0
-->

> Stability: 0 - Deprecated

The default encoding to use for functions that can take either strings
or [buffers][`Buffer`]. The default value is `'buffer'`, which makes methods
default to [`Buffer`][] objects.

The `crypto.DEFAULT_ENCODING` mechanism is provided for backward compatibility
with legacy programs that expect `'latin1'` to be the default encoding.

New applications should expect the default to be `'buffer'`.

This property is deprecated.

### `crypto.fips`

<!-- YAML
added: v6.0.0
deprecated: v10.0.0
-->

> Stability: 0 - Deprecated

Property for checking and controlling whether a FIPS compliant crypto provider
is currently in use. Setting to true requires a FIPS build of Node.js.

This property is deprecated. Please use `crypto.setFips()` and
`crypto.getFips()` instead.

### `crypto.checkPrime(candidate[, options, [callback]])`

<!-- YAML
added: v15.8.0
-->

* `candidate` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  A possible prime encoded as a sequence of big endian octets of arbitrary
  length.
* `options` {Object}
  * `checks` {number} The number of Miller-Rabin probabilistic primality
    iterations to perform. When the value is `0` (zero), a number of checks
    is used that yields a false positive rate of at most 2<sup>-64</sup> for
    random input. Care must be used when selecting a number of checks. Refer
    to the OpenSSL documentation for the [`BN_is_prime_ex`][] function `nchecks`
    options for more details. **Default:** `0`
* `callback` {Function}
  * `err` {Error} Set to an {Error} object if an error occurred during check.
  * `result` {boolean} `true` if the candidate is a prime with an error
    probability less than `0.25 ** options.checks`.

Checks the primality of the `candidate`.

### `crypto.checkPrimeSync(candidate[, options])`

<!-- YAML
added: v15.8.0
-->

* `candidate` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  A possible prime encoded as a sequence of big endian octets of arbitrary
  length.
* `options` {Object}
  * `checks` {number} The number of Miller-Rabin probabilistic primality
    iterations to perform. When the value is `0` (zero), a number of checks
    is used that yields a false positive rate of at most 2<sup>-64</sup> for
    random input. Care must be used when selecting a number of checks. Refer
    to the OpenSSL documentation for the [`BN_is_prime_ex`][] function `nchecks`
    options for more details. **Default:** `0`
* Returns: {boolean} `true` if the candidate is a prime with an error
  probability less than `0.25 ** options.checks`.

Checks the primality of the `candidate`.

### `crypto.createCipher(algorithm, password[, options])`

<!-- YAML
added: v0.1.94
deprecated: v10.0.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The password argument can be an ArrayBuffer and is limited to
                 a maximum of 2 ** 31 - 1 bytes.
  - version: v10.10.0
    pr-url: https://github.com/nodejs/node/pull/21447
    description: Ciphers in OCB mode are now supported.
  - version: v10.2.0
    pr-url: https://github.com/nodejs/node/pull/20235
    description: The `authTagLength` option can now be used to produce shorter
                 authentication tags in GCM mode and defaults to 16 bytes.
-->

> Stability: 0 - Deprecated: Use [`crypto.createCipheriv()`][] instead.

* `algorithm` {string}
* `password` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `options` {Object} [`stream.transform` options][]
* Returns: {Cipher}

Creates and returns a `Cipher` object that uses the given `algorithm` and
`password`.

The `options` argument controls stream behavior and is optional except when a
cipher in CCM or OCB mode is used (e.g. `'aes-128-ccm'`). In that case, the
`authTagLength` option is required and specifies the length of the
authentication tag in bytes, see [CCM mode][]. In GCM mode, the `authTagLength`
option is not required but can be used to set the length of the authentication
tag that will be returned by `getAuthTag()` and defaults to 16 bytes.

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On
recent OpenSSL releases, `openssl list -cipher-algorithms`
(`openssl list-cipher-algorithms` for older versions of OpenSSL) will
display the available cipher algorithms.

The `password` is used to derive the cipher key and initialization vector (IV).
The value must be either a `'latin1'` encoded string, a [`Buffer`][], a
`TypedArray`, or a `DataView`.

The implementation of `crypto.createCipher()` derives keys using the OpenSSL
function [`EVP_BytesToKey`][] with the digest algorithm set to MD5, one
iteration, and no salt. The lack of salt allows dictionary attacks as the same
password always creates the same key. The low iteration count and
non-cryptographically secure hash algorithm allow passwords to be tested very
rapidly.

In line with OpenSSL's recommendation to use a more modern algorithm instead of
[`EVP_BytesToKey`][] it is recommended that developers derive a key and IV on
their own using [`crypto.scrypt()`][] and to use [`crypto.createCipheriv()`][]
to create the `Cipher` object. Users should not use ciphers with counter mode
(e.g. CTR, GCM, or CCM) in `crypto.createCipher()`. A warning is emitted when
they are used in order to avoid the risk of IV reuse that causes
vulnerabilities. For the case when IV is reused in GCM, see [Nonce-Disrespecting
Adversaries][] for details.

### `crypto.createCipheriv(algorithm, key, iv[, options])`

<!-- YAML
added: v0.1.94
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The password and iv arguments can be an ArrayBuffer and are
                 each limited to a maximum of 2 ** 31 - 1 bytes.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: The `key` argument can now be a `KeyObject`.
  - version:
     - v11.2.0
     - v10.17.0
    pr-url: https://github.com/nodejs/node/pull/24081
    description: The cipher `chacha20-poly1305` is now supported.
  - version: v10.10.0
    pr-url: https://github.com/nodejs/node/pull/21447
    description: Ciphers in OCB mode are now supported.
  - version: v10.2.0
    pr-url: https://github.com/nodejs/node/pull/20235
    description: The `authTagLength` option can now be used to produce shorter
                 authentication tags in GCM mode and defaults to 16 bytes.
  - version: v9.9.0
    pr-url: https://github.com/nodejs/node/pull/18644
    description: The `iv` parameter may now be `null` for ciphers which do not
                 need an initialization vector.
-->

* `algorithm` {string}
* `key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
* `iv` {string|ArrayBuffer|Buffer|TypedArray|DataView|null}
* `options` {Object} [`stream.transform` options][]
* Returns: {Cipher}

Creates and returns a `Cipher` object, with the given `algorithm`, `key` and
initialization vector (`iv`).

The `options` argument controls stream behavior and is optional except when a
cipher in CCM or OCB mode is used (e.g. `'aes-128-ccm'`). In that case, the
`authTagLength` option is required and specifies the length of the
authentication tag in bytes, see [CCM mode][]. In GCM mode, the `authTagLength`
option is not required but can be used to set the length of the authentication
tag that will be returned by `getAuthTag()` and defaults to 16 bytes.

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On
recent OpenSSL releases, `openssl list -cipher-algorithms`
(`openssl list-cipher-algorithms` for older versions of OpenSSL) will
display the available cipher algorithms.

The `key` is the raw key used by the `algorithm` and `iv` is an
[initialization vector][]. Both arguments must be `'utf8'` encoded strings,
[Buffers][`Buffer`], `TypedArray`, or `DataView`s. The `key` may optionally be
a [`KeyObject`][] of type `secret`. If the cipher does not need
an initialization vector, `iv` may be `null`.

When passing strings for `key` or `iv`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

Initialization vectors should be unpredictable and unique; ideally, they will be
cryptographically random. They do not have to be secret: IVs are typically just
added to ciphertext messages unencrypted. It may sound contradictory that
something has to be unpredictable and unique, but does not have to be secret;
remember that an attacker must not be able to predict ahead of time what a
given IV will be.

### `crypto.createDecipher(algorithm, password[, options])`

<!-- YAML
added: v0.1.94
deprecated: v10.0.0
changes:
  - version: v10.10.0
    pr-url: https://github.com/nodejs/node/pull/21447
    description: Ciphers in OCB mode are now supported.
-->

> Stability: 0 - Deprecated: Use [`crypto.createDecipheriv()`][] instead.

* `algorithm` {string}
* `password` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `options` {Object} [`stream.transform` options][]
* Returns: {Decipher}

Creates and returns a `Decipher` object that uses the given `algorithm` and
`password` (key).

The `options` argument controls stream behavior and is optional except when a
cipher in CCM or OCB mode is used (e.g. `'aes-128-ccm'`). In that case, the
`authTagLength` option is required and specifies the length of the
authentication tag in bytes, see [CCM mode][].

The implementation of `crypto.createDecipher()` derives keys using the OpenSSL
function [`EVP_BytesToKey`][] with the digest algorithm set to MD5, one
iteration, and no salt. The lack of salt allows dictionary attacks as the same
password always creates the same key. The low iteration count and
non-cryptographically secure hash algorithm allow passwords to be tested very
rapidly.

In line with OpenSSL's recommendation to use a more modern algorithm instead of
[`EVP_BytesToKey`][] it is recommended that developers derive a key and IV on
their own using [`crypto.scrypt()`][] and to use [`crypto.createDecipheriv()`][]
to create the `Decipher` object.

### `crypto.createDecipheriv(algorithm, key, iv[, options])`

<!-- YAML
added: v0.1.94
changes:
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: The `key` argument can now be a `KeyObject`.
  - version:
     - v11.2.0
     - v10.17.0
    pr-url: https://github.com/nodejs/node/pull/24081
    description: The cipher `chacha20-poly1305` is now supported.
  - version: v10.10.0
    pr-url: https://github.com/nodejs/node/pull/21447
    description: Ciphers in OCB mode are now supported.
  - version: v10.2.0
    pr-url: https://github.com/nodejs/node/pull/20039
    description: The `authTagLength` option can now be used to restrict accepted
                 GCM authentication tag lengths.
  - version: v9.9.0
    pr-url: https://github.com/nodejs/node/pull/18644
    description: The `iv` parameter may now be `null` for ciphers which do not
                 need an initialization vector.
-->

* `algorithm` {string}
* `key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
* `iv` {string|ArrayBuffer|Buffer|TypedArray|DataView|null}
* `options` {Object} [`stream.transform` options][]
* Returns: {Decipher}

Creates and returns a `Decipher` object that uses the given `algorithm`, `key`
and initialization vector (`iv`).

The `options` argument controls stream behavior and is optional except when a
cipher in CCM or OCB mode is used (e.g. `'aes-128-ccm'`). In that case, the
`authTagLength` option is required and specifies the length of the
authentication tag in bytes, see [CCM mode][]. In GCM mode, the `authTagLength`
option is not required but can be used to restrict accepted authentication tags
to those with the specified length.

The `algorithm` is dependent on OpenSSL, examples are `'aes192'`, etc. On
recent OpenSSL releases, `openssl list -cipher-algorithms`
(`openssl list-cipher-algorithms` for older versions of OpenSSL) will
display the available cipher algorithms.

The `key` is the raw key used by the `algorithm` and `iv` is an
[initialization vector][]. Both arguments must be `'utf8'` encoded strings,
[Buffers][`Buffer`], `TypedArray`, or `DataView`s. The `key` may optionally be
a [`KeyObject`][] of type `secret`. If the cipher does not need
an initialization vector, `iv` may be `null`.

When passing strings for `key` or `iv`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

Initialization vectors should be unpredictable and unique; ideally, they will be
cryptographically random. They do not have to be secret: IVs are typically just
added to ciphertext messages unencrypted. It may sound contradictory that
something has to be unpredictable and unique, but does not have to be secret;
remember that an attacker must not be able to predict ahead of time what a given
IV will be.

### `crypto.createDiffieHellman(prime[, primeEncoding][, generator][, generatorEncoding])`

<!-- YAML
added: v0.11.12
changes:
  - version: v8.0.0
    pr-url: https://github.com/nodejs/node/pull/12223
    description: The `prime` argument can be any `TypedArray` or `DataView` now.
  - version: v8.0.0
    pr-url: https://github.com/nodejs/node/pull/11983
    description: The `prime` argument can be a `Uint8Array` now.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default for the encoding parameters changed
                 from `binary` to `utf8`.
-->

* `prime` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `primeEncoding` {string} The [encoding][] of the `prime` string.
* `generator` {number|string|ArrayBuffer|Buffer|TypedArray|DataView}
  **Default:** `2`
* `generatorEncoding` {string} The [encoding][] of the `generator` string.
* Returns: {DiffieHellman}

Creates a `DiffieHellman` key exchange object using the supplied `prime` and an
optional specific `generator`.

The `generator` argument can be a number, string, or [`Buffer`][]. If
`generator` is not specified, the value `2` is used.

If `primeEncoding` is specified, `prime` is expected to be a string; otherwise
a [`Buffer`][], `TypedArray`, or `DataView` is expected.

If `generatorEncoding` is specified, `generator` is expected to be a string;
otherwise a number, [`Buffer`][], `TypedArray`, or `DataView` is expected.

### `crypto.createDiffieHellman(primeLength[, generator])`

<!-- YAML
added: v0.5.0
-->

* `primeLength` {number}
* `generator` {number} **Default:** `2`
* Returns: {DiffieHellman}

Creates a `DiffieHellman` key exchange object and generates a prime of
`primeLength` bits using an optional specific numeric `generator`.
If `generator` is not specified, the value `2` is used.

### `crypto.createDiffieHellmanGroup(name)`

<!-- YAML
added: v0.9.3
-->

* `name` {string}
* Returns: {DiffieHellmanGroup}

An alias for [`crypto.getDiffieHellman()`][]

### `crypto.createECDH(curveName)`

<!-- YAML
added: v0.11.14
-->

* `curveName` {string}
* Returns: {ECDH}

Creates an Elliptic Curve Diffie-Hellman (`ECDH`) key exchange object using a
predefined curve specified by the `curveName` string. Use
[`crypto.getCurves()`][] to obtain a list of available curve names. On recent
OpenSSL releases, `openssl ecparam -list_curves` will also display the name
and description of each available elliptic curve.

### `crypto.createHash(algorithm[, options])`

<!-- YAML
added: v0.1.92
changes:
  - version: v12.8.0
    pr-url: https://github.com/nodejs/node/pull/28805
    description: The `outputLength` option was added for XOF hash functions.
-->

* `algorithm` {string}
* `options` {Object} [`stream.transform` options][]
* Returns: {Hash}

Creates and returns a `Hash` object that can be used to generate hash digests
using the given `algorithm`. Optional `options` argument controls stream
behavior. For XOF hash functions such as `'shake256'`, the `outputLength` option
can be used to specify the desired output length in bytes.

The `algorithm` is dependent on the available algorithms supported by the
version of OpenSSL on the platform. Examples are `'sha256'`, `'sha512'`, etc.
On recent releases of OpenSSL, `openssl list -digest-algorithms`
(`openssl list-message-digest-algorithms` for older versions of OpenSSL) will
display the available digest algorithms.

Example: generating the sha256 sum of a file

```mjs
import {
  createReadStream
} from 'fs';
import { argv } from 'process';
const {
  createHash
} = await import('crypto');

const filename = argv[2];

const hash = createHash('sha256');

const input = createReadStream(filename);
input.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = input.read();
  if (data)
    hash.update(data);
  else {
    console.log(`${hash.digest('hex')} ${filename}`);
  }
});
```

```cjs
const {
  createReadStream,
} = require('fs');
const {
  createHash,
} = require('crypto');
const { argv } = require('process');

const filename = argv[2];

const hash = createHash('sha256');

const input = createReadStream(filename);
input.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = input.read();
  if (data)
    hash.update(data);
  else {
    console.log(`${hash.digest('hex')} ${filename}`);
  }
});
```

### `crypto.createHmac(algorithm, key[, options])`

<!-- YAML
added: v0.1.94
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The key can also be an ArrayBuffer or CryptoKey. The
                 encoding option was added. The key cannot contain
                 more than 2 ** 32 - 1 bytes.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: The `key` argument can now be a `KeyObject`.
-->

* `algorithm` {string}
* `key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
* `options` {Object} [`stream.transform` options][]
  * `encoding` {string} The string encoding to use when `key` is a string.
* Returns: {Hmac}

Creates and returns an `Hmac` object that uses the given `algorithm` and `key`.
Optional `options` argument controls stream behavior.

The `algorithm` is dependent on the available algorithms supported by the
version of OpenSSL on the platform. Examples are `'sha256'`, `'sha512'`, etc.
On recent releases of OpenSSL, `openssl list -digest-algorithms`
(`openssl list-message-digest-algorithms` for older versions of OpenSSL) will
display the available digest algorithms.

The `key` is the HMAC key used to generate the cryptographic HMAC hash. If it is
a [`KeyObject`][], its type must be `secret`.

Example: generating the sha256 HMAC of a file

```mjs
import {
  createReadStream
} from 'fs';
import { argv } from 'process';
const {
  createHmac
} = await import('crypto');

const filename = argv[2];

const hmac = createHmac('sha256', 'a secret');

const input = createReadStream(filename);
input.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = input.read();
  if (data)
    hmac.update(data);
  else {
    console.log(`${hmac.digest('hex')} ${filename}`);
  }
});
```

```cjs
const {
  createReadStream,
} = require('fs');
const {
  createHmac,
} = require('crypto');
const { argv } = require('process');

const filename = argv[2];

const hmac = createHmac('sha256', 'a secret');

const input = createReadStream(filename);
input.on('readable', () => {
  // Only one element is going to be produced by the
  // hash stream.
  const data = input.read();
  if (data)
    hmac.update(data);
  else {
    console.log(`${hmac.digest('hex')} ${filename}`);
  }
});
```

### `crypto.createPrivateKey(key)`

<!-- YAML
added: v11.6.0
changes:
  - version: v15.12.0
    pr-url: https://github.com/nodejs/node/pull/37254
    description: The key can also be a JWK object.
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The key can also be an ArrayBuffer. The encoding option was
                 added. The key cannot contain more than 2 ** 32 - 1 bytes.
-->

<!--lint disable maximum-line-length remark-lint-->

* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView}
  * `key`: {string|ArrayBuffer|Buffer|TypedArray|DataView|Object} The key
    material, either in PEM, DER, or JWK format.
  * `format`: {string} Must be `'pem'`, `'der'`, or '`'jwk'`.
    **Default:** `'pem'`.
  * `type`: {string} Must be `'pkcs1'`, `'pkcs8'` or `'sec1'`. This option is
    required only if the `format` is `'der'` and ignored otherwise.
  * `passphrase`: {string | Buffer} The passphrase to use for decryption.
  * `encoding`: {string} The string encoding to use when `key` is a string.
* Returns: {KeyObject}

<!--lint enable maximum-line-length remark-lint-->

Creates and returns a new key object containing a private key. If `key` is a
string or `Buffer`, `format` is assumed to be `'pem'`; otherwise, `key`
must be an object with the properties described above.

If the private key is encrypted, a `passphrase` must be specified. The length
of the passphrase is limited to 1024 bytes.

### `crypto.createPublicKey(key)`

<!-- YAML
added: v11.6.0
changes:
  - version: v15.12.0
    pr-url: https://github.com/nodejs/node/pull/37254
    description: The key can also be a JWK object.
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The key can also be an ArrayBuffer. The encoding option was
                 added. The key cannot contain more than 2 ** 32 - 1 bytes.
  - version: v11.13.0
    pr-url: https://github.com/nodejs/node/pull/26278
    description: The `key` argument can now be a `KeyObject` with type
                 `private`.
  - version: v11.7.0
    pr-url: https://github.com/nodejs/node/pull/25217
    description: The `key` argument can now be a private key.
-->

<!--lint disable maximum-line-length remark-lint-->

* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView}
  * `key`: {string|ArrayBuffer|Buffer|TypedArray|DataView|Object} The key
    material, either in PEM, DER, or JWK format.
  * `format`: {string} Must be `'pem'`, `'der'`, or `'jwk'`.
    **Default:** `'pem'`.
  * `type`: {string} Must be `'pkcs1'` or `'spki'`. This option is
    required only if the `format` is `'der'` and ignored otherwise.
  * `encoding` {string} The string encoding to use when `key` is a string.
* Returns: {KeyObject}

<!--lint enable maximum-line-length remark-lint-->

Creates and returns a new key object containing a public key. If `key` is a
string or `Buffer`, `format` is assumed to be `'pem'`; if `key` is a `KeyObject`
with type `'private'`, the public key is derived from the given private key;
otherwise, `key` must be an object with the properties described above.

If the format is `'pem'`, the `'key'` may also be an X.509 certificate.

Because public keys can be derived from private keys, a private key may be
passed instead of a public key. In that case, this function behaves as if
[`crypto.createPrivateKey()`][] had been called, except that the type of the
returned `KeyObject` will be `'public'` and that the private key cannot be
extracted from the returned `KeyObject`. Similarly, if a `KeyObject` with type
`'private'` is given, a new `KeyObject` with type `'public'` will be returned
and it will be impossible to extract the private key from the returned object.

### `crypto.createSecretKey(key[, encoding])`

<!-- YAML
added: v11.6.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The key can also be an ArrayBuffer or string. The encoding
                 argument was added. The key cannot contain more than
                 2 ** 32 - 1 bytes.
-->

* `key` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `encoding` {string} The string encoding when `key` is a string.
* Returns: {KeyObject}

Creates and returns a new key object containing a secret key for symmetric
encryption or `Hmac`.

### `crypto.createSign(algorithm[, options])`

<!-- YAML
added: v0.1.92
-->

* `algorithm` {string}
* `options` {Object} [`stream.Writable` options][]
* Returns: {Sign}

Creates and returns a `Sign` object that uses the given `algorithm`. Use
[`crypto.getHashes()`][] to obtain the names of the available digest algorithms.
Optional `options` argument controls the `stream.Writable` behavior.

In some cases, a `Sign` instance can be created using the name of a signature
algorithm, such as `'RSA-SHA256'`, instead of a digest algorithm. This will use
the corresponding digest algorithm. This does not work for all signature
algorithms, such as `'ecdsa-with-SHA256'`, so it is best to always use digest
algorithm names.

### `crypto.createVerify(algorithm[, options])`

<!-- YAML
added: v0.1.92
-->

* `algorithm` {string}
* `options` {Object} [`stream.Writable` options][]
* Returns: {Verify}

Creates and returns a `Verify` object that uses the given algorithm.
Use [`crypto.getHashes()`][] to obtain an array of names of the available
signing algorithms. Optional `options` argument controls the
`stream.Writable` behavior.

In some cases, a `Verify` instance can be created using the name of a signature
algorithm, such as `'RSA-SHA256'`, instead of a digest algorithm. This will use
the corresponding digest algorithm. This does not work for all signature
algorithms, such as `'ecdsa-with-SHA256'`, so it is best to always use digest
algorithm names.

### `crypto.diffieHellman(options)`

<!-- YAML
added:
 - v13.9.0
 - v12.17.0
-->

* `options`: {Object}
  * `privateKey`: {KeyObject}
  * `publicKey`: {KeyObject}
* Returns: {Buffer}

Computes the Diffie-Hellman secret based on a `privateKey` and a `publicKey`.
Both keys must have the same `asymmetricKeyType`, which must be one of `'dh'`
(for Diffie-Hellman), `'ec'` (for ECDH), `'x448'`, or `'x25519'` (for ECDH-ES).

### `crypto.generateKey(type, options, callback)`

<!-- YAML
added: v15.0.0
-->

* `type`: {string} The intended use of the generated secret key. Currently
  accepted values are `'hmac'` and `'aes'`.
* `options`: {Object}
  * `length`: {number} The bit length of the key to generate. This must be a
    value greater than 0.
    * If `type` is `'hmac'`, the minimum is 1, and the maximum length is
      2<sup>31</sup>-1. If the value is not a multiple of 8, the generated
      key will be truncated to `Math.floor(length / 8)`.
    * If `type` is `'aes'`, the length must be one of `128`, `192`, or `256`.
* `callback`: {Function}
  * `err`: {Error}
  * `key`: {KeyObject}

Asynchronously generates a new random secret key of the given `length`. The
`type` will determine which validations will be performed on the `length`.

```mjs
const {
  generateKey
} = await import('crypto');

generateKey('hmac', { length: 64 }, (err, key) => {
  if (err) throw err;
  console.log(key.export().toString('hex'));  // 46e..........620
});
```

```cjs
const {
  generateKey,
} = require('crypto');

generateKey('hmac', { length: 64 }, (err, key) => {
  if (err) throw err;
  console.log(key.export().toString('hex'));  // 46e..........620
});
```

### `crypto.generateKeyPair(type, options, callback)`

<!-- YAML
added: v10.12.0
changes:
  - version: v16.10.0
    pr-url: https://github.com/nodejs/node/pull/39927
    description: Add ability to define `RSASSA-PSS-params` sequence parameters
                 for RSA-PSS keys pairs.
  - version:
     - v13.9.0
     - v12.17.0
    pr-url: https://github.com/nodejs/node/pull/31178
    description: Add support for Diffie-Hellman.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26960
    description: Add support for RSA-PSS key pairs.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26774
    description: Add ability to generate X25519 and X448 key pairs.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26554
    description: Add ability to generate Ed25519 and Ed448 key pairs.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: The `generateKeyPair` and `generateKeyPairSync` functions now
                 produce key objects if no encoding was specified.
-->

* `type`: {string} Must be `'rsa'`, `'rsa-pss'`, `'dsa'`, `'ec'`, `'ed25519'`,
  `'ed448'`, `'x25519'`, `'x448'`, or `'dh'`.
* `options`: {Object}
  * `modulusLength`: {number} Key size in bits (RSA, DSA).
  * `publicExponent`: {number} Public exponent (RSA). **Default:** `0x10001`.
  * `hashAlgorithm`: {string} Name of the message digest (RSA-PSS).
  * `mgf1HashAlgorithm`: {string} Name of the message digest used by
    MGF1 (RSA-PSS).
  * `saltLength`: {number} Minimal salt length in bytes (RSA-PSS).
  * `divisorLength`: {number} Size of `q` in bits (DSA).
  * `namedCurve`: {string} Name of the curve to use (EC).
  * `prime`: {Buffer} The prime parameter (DH).
  * `primeLength`: {number} Prime length in bits (DH).
  * `generator`: {number} Custom generator (DH). **Default:** `2`.
  * `groupName`: {string} Diffie-Hellman group name (DH). See
    [`crypto.getDiffieHellman()`][].
  * `publicKeyEncoding`: {Object} See [`keyObject.export()`][].
  * `privateKeyEncoding`: {Object} See [`keyObject.export()`][].
* `callback`: {Function}
  * `err`: {Error}
  * `publicKey`: {string | Buffer | KeyObject}
  * `privateKey`: {string | Buffer | KeyObject}

Generates a new asymmetric key pair of the given `type`. RSA, RSA-PSS, DSA, EC,
Ed25519, Ed448, X25519, X448, and DH are currently supported.

If a `publicKeyEncoding` or `privateKeyEncoding` was specified, this function
behaves as if [`keyObject.export()`][] had been called on its result. Otherwise,
the respective part of the key is returned as a [`KeyObject`][].

It is recommended to encode public keys as `'spki'` and private keys as
`'pkcs8'` with encryption for long-term storage:

```mjs
const {
  generateKeyPair
} = await import('crypto');

generateKeyPair('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
    cipher: 'aes-256-cbc',
    passphrase: 'top secret'
  }
}, (err, publicKey, privateKey) => {
  // Handle errors and use the generated key pair.
});
```

```cjs
const {
  generateKeyPair,
} = require('crypto');

generateKeyPair('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
    cipher: 'aes-256-cbc',
    passphrase: 'top secret'
  }
}, (err, publicKey, privateKey) => {
  // Handle errors and use the generated key pair.
});
```

On completion, `callback` will be called with `err` set to `undefined` and
`publicKey` / `privateKey` representing the generated key pair.

If this method is invoked as its [`util.promisify()`][]ed version, it returns
a `Promise` for an `Object` with `publicKey` and `privateKey` properties.

### `crypto.generateKeyPairSync(type, options)`

<!-- YAML
added: v10.12.0
changes:
  - version: v16.10.0
    pr-url: https://github.com/nodejs/node/pull/39927
    description: Add ability to define `RSASSA-PSS-params` sequence parameters
                 for RSA-PSS keys pairs.
  - version:
     - v13.9.0
     - v12.17.0
    pr-url: https://github.com/nodejs/node/pull/31178
    description: Add support for Diffie-Hellman.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26960
    description: Add support for RSA-PSS key pairs.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26774
    description: Add ability to generate X25519 and X448 key pairs.
  - version: v12.0.0
    pr-url: https://github.com/nodejs/node/pull/26554
    description: Add ability to generate Ed25519 and Ed448 key pairs.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: The `generateKeyPair` and `generateKeyPairSync` functions now
                 produce key objects if no encoding was specified.
-->

* `type`: {string} Must be `'rsa'`, `'rsa-pss'`, `'dsa'`, `'ec'`, `'ed25519'`,
  `'ed448'`, `'x25519'`, `'x448'`, or `'dh'`.
* `options`: {Object}
  * `modulusLength`: {number} Key size in bits (RSA, DSA).
  * `publicExponent`: {number} Public exponent (RSA). **Default:** `0x10001`.
  * `hashAlgorithm`: {string} Name of the message digest (RSA-PSS).
  * `mgf1HashAlgorithm`: {string} Name of the message digest used by
    MGF1 (RSA-PSS).
  * `saltLength`: {number} Minimal salt length in bytes (RSA-PSS).
  * `divisorLength`: {number} Size of `q` in bits (DSA).
  * `namedCurve`: {string} Name of the curve to use (EC).
  * `prime`: {Buffer} The prime parameter (DH).
  * `primeLength`: {number} Prime length in bits (DH).
  * `generator`: {number} Custom generator (DH). **Default:** `2`.
  * `groupName`: {string} Diffie-Hellman group name (DH). See
    [`crypto.getDiffieHellman()`][].
  * `publicKeyEncoding`: {Object} See [`keyObject.export()`][].
  * `privateKeyEncoding`: {Object} See [`keyObject.export()`][].
* Returns: {Object}
  * `publicKey`: {string | Buffer | KeyObject}
  * `privateKey`: {string | Buffer | KeyObject}

Generates a new asymmetric key pair of the given `type`. RSA, RSA-PSS, DSA, EC,
Ed25519, Ed448, X25519, X448, and DH are currently supported.

If a `publicKeyEncoding` or `privateKeyEncoding` was specified, this function
behaves as if [`keyObject.export()`][] had been called on its result. Otherwise,
the respective part of the key is returned as a [`KeyObject`][].

When encoding public keys, it is recommended to use `'spki'`. When encoding
private keys, it is recommended to use `'pkcs8'` with a strong passphrase,
and to keep the passphrase confidential.

```mjs
const {
  generateKeyPairSync
} = await import('crypto');

const {
  publicKey,
  privateKey,
} = generateKeyPairSync('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
    cipher: 'aes-256-cbc',
    passphrase: 'top secret'
  }
});
```

```cjs
const {
  generateKeyPairSync,
} = require('crypto');

const {
  publicKey,
  privateKey,
} = generateKeyPairSync('rsa', {
  modulusLength: 4096,
  publicKeyEncoding: {
    type: 'spki',
    format: 'pem'
  },
  privateKeyEncoding: {
    type: 'pkcs8',
    format: 'pem',
    cipher: 'aes-256-cbc',
    passphrase: 'top secret'
  }
});
```

The return value `{ publicKey, privateKey }` represents the generated key pair.
When PEM encoding was selected, the respective key will be a string, otherwise
it will be a buffer containing the data encoded as DER.

### `crypto.generateKeySync(type, options)`

<!-- YAML
added: v15.0.0
-->

* `type`: {string} The intended use of the generated secret key. Currently
  accepted values are `'hmac'` and `'aes'`.
* `options`: {Object}
  * `length`: {number} The bit length of the key to generate.
    * If `type` is `'hmac'`, the minimum is 1, and the maximum length is
      2<sup>31</sup>-1. If the value is not a multiple of 8, the generated
      key will be truncated to `Math.floor(length / 8)`.
    * If `type` is `'aes'`, the length must be one of `128`, `192`, or `256`.
* Returns: {KeyObject}

Synchronously generates a new random secret key of the given `length`. The
`type` will determine which validations will be performed on the `length`.

```mjs
const {
  generateKeySync
} = await import('crypto');

const key = generateKeySync('hmac', { length: 64 });
console.log(key.export().toString('hex'));  // e89..........41e
```

```cjs
const {
  generateKeySync,
} = require('crypto');

const key = generateKeySync('hmac', { length: 64 });
console.log(key.export().toString('hex'));  // e89..........41e
```

### `crypto.generatePrime(size[, options[, callback]])`

<!-- YAML
added: v15.8.0
-->

* `size` {number} The size (in bits) of the prime to generate.
* `options` {Object}
  * `add` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  * `rem` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  * `safe` {boolean} **Default:** `false`.
  * `bigint` {boolean} When `true`, the generated prime is returned
    as a `bigint`.
* `callback` {Function}
  * `err` {Error}
  * `prime` {ArrayBuffer|bigint}

Generates a pseudorandom prime of `size` bits.

If `options.safe` is `true`, the prime will be a safe prime -- that is,
`(prime - 1) / 2` will also be a prime.

The `options.add` and `options.rem` parameters can be used to enforce additional
requirements, e.g., for Diffie-Hellman:

* If `options.add` and `options.rem` are both set, the prime will satisfy the
  condition that `prime % add = rem`.
* If only `options.add` is set and `options.safe` is not `true`, the prime will
  satisfy the condition that `prime % add = 1`.
* If only `options.add` is set and `options.safe` is set to `true`, the prime
  will instead satisfy the condition that `prime % add = 3`. This is necessary
  because `prime % add = 1` for `options.add > 2` would contradict the condition
  enforced by `options.safe`.
* `options.rem` is ignored if `options.add` is not given.

Both `options.add` and `options.rem` must be encoded as big-endian sequences
if given as an `ArrayBuffer`, `SharedArrayBuffer`, `TypedArray`, `Buffer`, or
`DataView`.

By default, the prime is encoded as a big-endian sequence of octets
in an {ArrayBuffer}. If the `bigint` option is `true`, then a {bigint}
is provided.

### `crypto.generatePrimeSync(size[, options])`

<!-- YAML
added: v15.8.0
-->

* `size` {number} The size (in bits) of the prime to generate.
* `options` {Object}
  * `add` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  * `rem` {ArrayBuffer|SharedArrayBuffer|TypedArray|Buffer|DataView|bigint}
  * `safe` {boolean} **Default:** `false`.
  * `bigint` {boolean} When `true`, the generated prime is returned
    as a `bigint`.
* Returns: {ArrayBuffer|bigint}

Generates a pseudorandom prime of `size` bits.

If `options.safe` is `true`, the prime will be a safe prime -- that is,
`(prime - 1) / 2` will also be a prime.

The `options.add` and `options.rem` parameters can be used to enforce additional
requirements, e.g., for Diffie-Hellman:

* If `options.add` and `options.rem` are both set, the prime will satisfy the
  condition that `prime % add = rem`.
* If only `options.add` is set and `options.safe` is not `true`, the prime will
  satisfy the condition that `prime % add = 1`.
* If only `options.add` is set and `options.safe` is set to `true`, the prime
  will instead satisfy the condition that `prime % add = 3`. This is necessary
  because `prime % add = 1` for `options.add > 2` would contradict the condition
  enforced by `options.safe`.
* `options.rem` is ignored if `options.add` is not given.

Both `options.add` and `options.rem` must be encoded as big-endian sequences
if given as an `ArrayBuffer`, `SharedArrayBuffer`, `TypedArray`, `Buffer`, or
`DataView`.

By default, the prime is encoded as a big-endian sequence of octets
in an {ArrayBuffer}. If the `bigint` option is `true`, then a {bigint}
is provided.

### `crypto.getCipherInfo(nameOrNid[, options])`

<!-- YAML
added: v15.0.0
-->

* `nameOrNid`: {string|number} The name or nid of the cipher to query.
* `options`: {Object}
  * `keyLength`: {number} A test key length.
  * `ivLength`: {number} A test IV length.
* Returns: {Object}
  * `name` {string} The name of the cipher
  * `nid` {number} The nid of the cipher
  * `blockSize` {number} The block size of the cipher in bytes. This property
    is omitted when `mode` is `'stream'`.
  * `ivLength` {number} The expected or default initialization vector length in
    bytes. This property is omitted if the cipher does not use an initialization
    vector.
  * `keyLength` {number} The expected or default key length in bytes.
  * `mode` {string} The cipher mode. One of `'cbc'`, `'ccm'`, `'cfb'`, `'ctr'`,
    `'ecb'`, `'gcm'`, `'ocb'`, `'ofb'`, `'stream'`, `'wrap'`, `'xts'`.

Returns information about a given cipher.

Some ciphers accept variable length keys and initialization vectors. By default,
the `crypto.getCipherInfo()` method will return the default values for these
ciphers. To test if a given key length or iv length is acceptable for given
cipher, use the `keyLength` and `ivLength` options. If the given values are
unacceptable, `undefined` will be returned.

### `crypto.getCiphers()`

<!-- YAML
added: v0.9.3
-->

* Returns: {string\[]} An array with the names of the supported cipher
  algorithms.

```mjs
const {
  getCiphers
} = await import('crypto');

console.log(getCiphers()); // ['aes-128-cbc', 'aes-128-ccm', ...]
```

```cjs
const {
  getCiphers,
} = require('crypto');

console.log(getCiphers()); // ['aes-128-cbc', 'aes-128-ccm', ...]
```

### `crypto.getCurves()`

<!-- YAML
added: v2.3.0
-->

* Returns: {string\[]} An array with the names of the supported elliptic curves.

```mjs
const {
  getCurves
} = await import('crypto');

console.log(getCurves()); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]
```

```cjs
const {
  getCurves,
} = require('crypto');

console.log(getCurves()); // ['Oakley-EC2N-3', 'Oakley-EC2N-4', ...]
```

### `crypto.getDiffieHellman(groupName)`

<!-- YAML
added: v0.7.5
-->

* `groupName` {string}
* Returns: {DiffieHellmanGroup}

Creates a predefined `DiffieHellmanGroup` key exchange object. The
supported groups are: `'modp1'`, `'modp2'`, `'modp5'` (defined in
[RFC 2412][], but see [Caveats][]) and `'modp14'`, `'modp15'`,
`'modp16'`, `'modp17'`, `'modp18'` (defined in [RFC 3526][]). The
returned object mimics the interface of objects created by
[`crypto.createDiffieHellman()`][], but will not allow changing
the keys (with [`diffieHellman.setPublicKey()`][], for example). The
advantage of using this method is that the parties do not have to
generate nor exchange a group modulus beforehand, saving both processor
and communication time.

Example (obtaining a shared secret):

```mjs
const {
  getDiffieHellman
} = await import('crypto');
const alice = getDiffieHellman('modp14');
const bob = getDiffieHellman('modp14');

alice.generateKeys();
bob.generateKeys();

const aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

/* aliceSecret and bobSecret should be the same */
console.log(aliceSecret === bobSecret);
```

```cjs
const {
  getDiffieHellman,
} = require('crypto');

const alice = getDiffieHellman('modp14');
const bob = getDiffieHellman('modp14');

alice.generateKeys();
bob.generateKeys();

const aliceSecret = alice.computeSecret(bob.getPublicKey(), null, 'hex');
const bobSecret = bob.computeSecret(alice.getPublicKey(), null, 'hex');

/* aliceSecret and bobSecret should be the same */
console.log(aliceSecret === bobSecret);
```

### `crypto.getFips()`

<!-- YAML
added: v10.0.0
-->

* Returns: {number} `1` if and only if a FIPS compliant crypto provider is
  currently in use, `0` otherwise. A future semver-major release may change
  the return type of this API to a {boolean}.

### `crypto.getHashes()`

<!-- YAML
added: v0.9.3
-->

* Returns: {string\[]} An array of the names of the supported hash algorithms,
  such as `'RSA-SHA256'`. Hash algorithms are also called "digest" algorithms.

```mjs
const {
  getHashes
} = await import('crypto');

console.log(getHashes()); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]
```

```cjs
const {
  getHashes,
} = require('crypto');

console.log(getHashes()); // ['DSA', 'DSA-SHA', 'DSA-SHA1', ...]
```

### `crypto.getRandomValues(typedArray)`

<!-- YAML
added: v17.4.0
-->

* `typedArray` {Buffer|TypedArray|DataView|ArrayBuffer}
* Returns: {Buffer|TypedArray|DataView|ArrayBuffer} Returns `typedArray`.

A convenient alias for [`crypto.webcrypto.getRandomValues()`][].

### `crypto.hkdf(digest, ikm, salt, info, keylen, callback)`

<!-- YAML
added: v15.0.0
-->

* `digest` {string} The digest algorithm to use.
* `ikm` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject} The input
  keying material. It must be at least one byte in length.
* `salt` {string|ArrayBuffer|Buffer|TypedArray|DataView} The salt value. Must
  be provided but can be zero-length.
* `info` {string|ArrayBuffer|Buffer|TypedArray|DataView} Additional info value.
  Must be provided but can be zero-length, and cannot be more than 1024 bytes.
* `keylen` {number} The length of the key to generate. Must be greater than 0.
  The maximum allowable value is `255` times the number of bytes produced by
  the selected digest function (e.g. `sha512` generates 64-byte hashes, making
  the maximum HKDF output 16320 bytes).
* `callback` {Function}
  * `err` {Error}
  * `derivedKey` {ArrayBuffer}

HKDF is a simple key derivation function defined in RFC 5869. The given `ikm`,
`salt` and `info` are used with the `digest` to derive a key of `keylen` bytes.

The supplied `callback` function is called with two arguments: `err` and
`derivedKey`. If an errors occurs while deriving the key, `err` will be set;
otherwise `err` will be `null`. The successfully generated `derivedKey` will
be passed to the callback as an {ArrayBuffer}. An error will be thrown if any
of the input arguments specify invalid values or types.

```mjs
import { Buffer } from 'buffer';
const {
  hkdf
} = await import('crypto');

hkdf('sha512', 'key', 'salt', 'info', 64, (err, derivedKey) => {
  if (err) throw err;
  console.log(Buffer.from(derivedKey).toString('hex'));  // '24156e2...5391653'
});
```

```cjs
const {
  hkdf,
} = require('crypto');
const { Buffer } = require('buffer');

hkdf('sha512', 'key', 'salt', 'info', 64, (err, derivedKey) => {
  if (err) throw err;
  console.log(Buffer.from(derivedKey).toString('hex'));  // '24156e2...5391653'
});
```

### `crypto.hkdfSync(digest, ikm, salt, info, keylen)`

<!-- YAML
added: v15.0.0
-->

* `digest` {string} The digest algorithm to use.
* `ikm` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject} The input
  keying material. It must be at least one byte in length.
* `salt` {string|ArrayBuffer|Buffer|TypedArray|DataView} The salt value. Must
  be provided but can be zero-length.
* `info` {string|ArrayBuffer|Buffer|TypedArray|DataView} Additional info value.
  Must be provided but can be zero-length, and cannot be more than 1024 bytes.
* `keylen` {number} The length of the key to generate. Must be greater than 0.
  The maximum allowable value is `255` times the number of bytes produced by
  the selected digest function (e.g. `sha512` generates 64-byte hashes, making
  the maximum HKDF output 16320 bytes).
* Returns: {ArrayBuffer}

Provides a synchronous HKDF key derivation function as defined in RFC 5869. The
given `ikm`, `salt` and `info` are used with the `digest` to derive a key of
`keylen` bytes.

The successfully generated `derivedKey` will be returned as an {ArrayBuffer}.

An error will be thrown if any of the input arguments specify invalid values or
types, or if the derived key cannot be generated.

```mjs
import { Buffer } from 'buffer';
const {
  hkdfSync
} = await import('crypto');

const derivedKey = hkdfSync('sha512', 'key', 'salt', 'info', 64);
console.log(Buffer.from(derivedKey).toString('hex'));  // '24156e2...5391653'
```

```cjs
const {
  hkdfSync,
} = require('crypto');
const { Buffer } = require('buffer');

const derivedKey = hkdfSync('sha512', 'key', 'salt', 'info', 64);
console.log(Buffer.from(derivedKey).toString('hex'));  // '24156e2...5391653'
```

### `crypto.pbkdf2(password, salt, iterations, keylen, digest, callback)`

<!-- YAML
added: v0.5.5
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The password and salt arguments can also be ArrayBuffer
                 instances.
  - version: v14.0.0
    pr-url: https://github.com/nodejs/node/pull/30578
    description: The `iterations` parameter is now restricted to positive
                 values. Earlier releases treated other values as one.
  - version: v8.0.0
    pr-url: https://github.com/nodejs/node/pull/11305
    description: The `digest` parameter is always required now.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/4047
    description: Calling this function without passing the `digest` parameter
                 is deprecated now and will emit a warning.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default encoding for `password` if it is a string changed
                 from `binary` to `utf8`.
-->

* `password` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `salt` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `iterations` {number}
* `keylen` {number}
* `digest` {string}
* `callback` {Function}
  * `err` {Error}
  * `derivedKey` {Buffer}

Provides an asynchronous Password-Based Key Derivation Function 2 (PBKDF2)
implementation. A selected HMAC digest algorithm specified by `digest` is
applied to derive a key of the requested byte length (`keylen`) from the
`password`, `salt` and `iterations`.

The supplied `callback` function is called with two arguments: `err` and
`derivedKey`. If an error occurs while deriving the key, `err` will be set;
otherwise `err` will be `null`. By default, the successfully generated
`derivedKey` will be passed to the callback as a [`Buffer`][]. An error will be
thrown if any of the input arguments specify invalid values or types.

If `digest` is `null`, `'sha1'` will be used. This behavior is deprecated,
please specify a `digest` explicitly.

The `iterations` argument must be a number set as high as possible. The
higher the number of iterations, the more secure the derived key will be,
but will take a longer amount of time to complete.

The `salt` should be as unique as possible. It is recommended that a salt is
random and at least 16 bytes long. See [NIST SP 800-132][] for details.

When passing strings for `password` or `salt`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

```mjs
const {
  pbkdf2
} = await import('crypto');

pbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...08d59ae'
});
```

```cjs
const {
  pbkdf2,
} = require('crypto');

pbkdf2('secret', 'salt', 100000, 64, 'sha512', (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...08d59ae'
});
```

The `crypto.DEFAULT_ENCODING` property can be used to change the way the
`derivedKey` is passed to the callback. This property, however, has been
deprecated and use should be avoided.

```mjs
import crypto from 'crypto';
crypto.DEFAULT_ENCODING = 'hex';
crypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey);  // '3745e48...aa39b34'
});
```

```cjs
const crypto = require('crypto');
crypto.DEFAULT_ENCODING = 'hex';
crypto.pbkdf2('secret', 'salt', 100000, 512, 'sha512', (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey);  // '3745e48...aa39b34'
});
```

An array of supported digest functions can be retrieved using
[`crypto.getHashes()`][].

This API uses libuv's threadpool, which can have surprising and
negative performance implications for some applications; see the
[`UV_THREADPOOL_SIZE`][] documentation for more information.

### `crypto.pbkdf2Sync(password, salt, iterations, keylen, digest)`

<!-- YAML
added: v0.9.3
changes:
  - version: v14.0.0
    pr-url: https://github.com/nodejs/node/pull/30578
    description: The `iterations` parameter is now restricted to positive
                 values. Earlier releases treated other values as one.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/4047
    description: Calling this function without passing the `digest` parameter
                 is deprecated now and will emit a warning.
  - version: v6.0.0
    pr-url: https://github.com/nodejs/node/pull/5522
    description: The default encoding for `password` if it is a string changed
                 from `binary` to `utf8`.
-->

* `password` {string|Buffer|TypedArray|DataView}
* `salt` {string|Buffer|TypedArray|DataView}
* `iterations` {number}
* `keylen` {number}
* `digest` {string}
* Returns: {Buffer}

Provides a synchronous Password-Based Key Derivation Function 2 (PBKDF2)
implementation. A selected HMAC digest algorithm specified by `digest` is
applied to derive a key of the requested byte length (`keylen`) from the
`password`, `salt` and `iterations`.

If an error occurs an `Error` will be thrown, otherwise the derived key will be
returned as a [`Buffer`][].

If `digest` is `null`, `'sha1'` will be used. This behavior is deprecated,
please specify a `digest` explicitly.

The `iterations` argument must be a number set as high as possible. The
higher the number of iterations, the more secure the derived key will be,
but will take a longer amount of time to complete.

The `salt` should be as unique as possible. It is recommended that a salt is
random and at least 16 bytes long. See [NIST SP 800-132][] for details.

When passing strings for `password` or `salt`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

```mjs
const {
  pbkdf2Sync
} = await import('crypto');

const key = pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');
console.log(key.toString('hex'));  // '3745e48...08d59ae'
```

```cjs
const {
  pbkdf2Sync,
} = require('crypto');

const key = pbkdf2Sync('secret', 'salt', 100000, 64, 'sha512');
console.log(key.toString('hex'));  // '3745e48...08d59ae'
```

The `crypto.DEFAULT_ENCODING` property may be used to change the way the
`derivedKey` is returned. This property, however, is deprecated and use
should be avoided.

```mjs
import crypto from 'crypto';
crypto.DEFAULT_ENCODING = 'hex';
const key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');
console.log(key);  // '3745e48...aa39b34'
```

```cjs
const crypto = require('crypto');
crypto.DEFAULT_ENCODING = 'hex';
const key = crypto.pbkdf2Sync('secret', 'salt', 100000, 512, 'sha512');
console.log(key);  // '3745e48...aa39b34'
```

An array of supported digest functions can be retrieved using
[`crypto.getHashes()`][].

### `crypto.privateDecrypt(privateKey, buffer)`

<!-- YAML
added: v0.11.14
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: Added string, ArrayBuffer, and CryptoKey as allowable key
                 types. The oaepLabel can be an ArrayBuffer. The buffer can
                 be a string or ArrayBuffer. All types that accept buffers
                 are limited to a maximum of 2 ** 31 - 1 bytes.
  - version: v12.11.0
    pr-url: https://github.com/nodejs/node/pull/29489
    description: The `oaepLabel` option was added.
  - version: v12.9.0
    pr-url: https://github.com/nodejs/node/pull/28335
    description: The `oaepHash` option was added.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: This function now supports key objects.
-->

<!--lint disable maximum-line-length remark-lint-->

* `privateKey` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `oaepHash` {string} The hash function to use for OAEP padding and MGF1.
    **Default:** `'sha1'`
  * `oaepLabel` {string|ArrayBuffer|Buffer|TypedArray|DataView} The label to
    use for OAEP padding. If not specified, no label is used.
  * `padding` {crypto.constants} An optional padding value defined in
    `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`,
    `crypto.constants.RSA_PKCS1_PADDING`, or
    `crypto.constants.RSA_PKCS1_OAEP_PADDING`.
* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* Returns: {Buffer} A new `Buffer` with the decrypted content.

<!--lint enable maximum-line-length remark-lint-->

Decrypts `buffer` with `privateKey`. `buffer` was previously encrypted using
the corresponding public key, for example using [`crypto.publicEncrypt()`][].

If `privateKey` is not a [`KeyObject`][], this function behaves as if
`privateKey` had been passed to [`crypto.createPrivateKey()`][]. If it is an
object, the `padding` property can be passed. Otherwise, this function uses
`RSA_PKCS1_OAEP_PADDING`.

### `crypto.privateEncrypt(privateKey, buffer)`

<!-- YAML
added: v1.1.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: Added string, ArrayBuffer, and CryptoKey as allowable key
                 types. The passphrase can be an ArrayBuffer. The buffer can
                 be a string or ArrayBuffer. All types that accept buffers
                 are limited to a maximum of 2 ** 31 - 1 bytes.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: This function now supports key objects.
-->

<!--lint disable maximum-line-length remark-lint-->

* `privateKey` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
    A PEM encoded private key.
  * `passphrase` {string|ArrayBuffer|Buffer|TypedArray|DataView} An optional
    passphrase for the private key.
  * `padding` {crypto.constants} An optional padding value defined in
    `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING` or
    `crypto.constants.RSA_PKCS1_PADDING`.
  * `encoding` {string} The string encoding to use when `buffer`, `key`,
    or `passphrase` are strings.
* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* Returns: {Buffer} A new `Buffer` with the encrypted content.

<!--lint enable maximum-line-length remark-lint-->

Encrypts `buffer` with `privateKey`. The returned data can be decrypted using
the corresponding public key, for example using [`crypto.publicDecrypt()`][].

If `privateKey` is not a [`KeyObject`][], this function behaves as if
`privateKey` had been passed to [`crypto.createPrivateKey()`][]. If it is an
object, the `padding` property can be passed. Otherwise, this function uses
`RSA_PKCS1_PADDING`.

### `crypto.publicDecrypt(key, buffer)`

<!-- YAML
added: v1.1.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: Added string, ArrayBuffer, and CryptoKey as allowable key
                 types. The passphrase can be an ArrayBuffer. The buffer can
                 be a string or ArrayBuffer. All types that accept buffers
                 are limited to a maximum of 2 ** 31 - 1 bytes.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: This function now supports key objects.
-->

<!--lint disable maximum-line-length remark-lint-->

* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `passphrase` {string|ArrayBuffer|Buffer|TypedArray|DataView} An optional
    passphrase for the private key.
  * `padding` {crypto.constants} An optional padding value defined in
    `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING` or
    `crypto.constants.RSA_PKCS1_PADDING`.
  * `encoding` {string} The string encoding to use when `buffer`, `key`,
    or `passphrase` are strings.
* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* Returns: {Buffer} A new `Buffer` with the decrypted content.

<!--lint enable maximum-line-length remark-lint-->

Decrypts `buffer` with `key`.`buffer` was previously encrypted using
the corresponding private key, for example using [`crypto.privateEncrypt()`][].

If `key` is not a [`KeyObject`][], this function behaves as if
`key` had been passed to [`crypto.createPublicKey()`][]. If it is an
object, the `padding` property can be passed. Otherwise, this function uses
`RSA_PKCS1_PADDING`.

Because RSA public keys can be derived from private keys, a private key may
be passed instead of a public key.

### `crypto.publicEncrypt(key, buffer)`

<!-- YAML
added: v0.11.14
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: Added string, ArrayBuffer, and CryptoKey as allowable key
                 types. The oaepLabel and passphrase can be ArrayBuffers. The
                 buffer can be a string or ArrayBuffer. All types that accept
                 buffers are limited to a maximum of 2 ** 31 - 1 bytes.
  - version: v12.11.0
    pr-url: https://github.com/nodejs/node/pull/29489
    description: The `oaepLabel` option was added.
  - version: v12.9.0
    pr-url: https://github.com/nodejs/node/pull/28335
    description: The `oaepHash` option was added.
  - version: v11.6.0
    pr-url: https://github.com/nodejs/node/pull/24234
    description: This function now supports key objects.
-->

<!--lint disable maximum-line-length remark-lint-->

* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
  * `key` {string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
    A PEM encoded public or private key, {KeyObject}, or {CryptoKey}.
  * `oaepHash` {string} The hash function to use for OAEP padding and MGF1.
    **Default:** `'sha1'`
  * `oaepLabel` {string|ArrayBuffer|Buffer|TypedArray|DataView} The label to
    use for OAEP padding. If not specified, no label is used.
  * `passphrase` {string|ArrayBuffer|Buffer|TypedArray|DataView} An optional
    passphrase for the private key.
  * `padding` {crypto.constants} An optional padding value defined in
    `crypto.constants`, which may be: `crypto.constants.RSA_NO_PADDING`,
    `crypto.constants.RSA_PKCS1_PADDING`, or
    `crypto.constants.RSA_PKCS1_OAEP_PADDING`.
  * `encoding` {string} The string encoding to use when `buffer`, `key`,
    `oaepLabel`, or `passphrase` are strings.
* `buffer` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* Returns: {Buffer} A new `Buffer` with the encrypted content.

<!--lint enable maximum-line-length remark-lint-->

Encrypts the content of `buffer` with `key` and returns a new
[`Buffer`][] with encrypted content. The returned data can be decrypted using
the corresponding private key, for example using [`crypto.privateDecrypt()`][].

If `key` is not a [`KeyObject`][], this function behaves as if
`key` had been passed to [`crypto.createPublicKey()`][]. If it is an
object, the `padding` property can be passed. Otherwise, this function uses
`RSA_PKCS1_OAEP_PADDING`.

Because RSA public keys can be derived from private keys, a private key may
be passed instead of a public key.

### `crypto.randomBytes(size[, callback])`

<!-- YAML
added: v0.5.8
changes:
  - version: v9.0.0
    pr-url: https://github.com/nodejs/node/pull/16454
    description: Passing `null` as the `callback` argument now throws
                 `ERR_INVALID_CALLBACK`.
-->

* `size` {number} The number of bytes to generate.  The `size` must
  not be larger than `2**31 - 1`.
* `callback` {Function}
  * `err` {Error}
  * `buf` {Buffer}
* Returns: {Buffer} if the `callback` function is not provided.

Generates cryptographically strong pseudorandom data. The `size` argument
is a number indicating the number of bytes to generate.

If a `callback` function is provided, the bytes are generated asynchronously
and the `callback` function is invoked with two arguments: `err` and `buf`.
If an error occurs, `err` will be an `Error` object; otherwise it is `null`. The
`buf` argument is a [`Buffer`][] containing the generated bytes.

```mjs
// Asynchronous
const {
  randomBytes
} = await import('crypto');

randomBytes(256, (err, buf) => {
  if (err) throw err;
  console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);
});
```

```cjs
// Asynchronous
const {
  randomBytes,
} = require('crypto');

randomBytes(256, (err, buf) => {
  if (err) throw err;
  console.log(`${buf.length} bytes of random data: ${buf.toString('hex')}`);
});
```

If the `callback` function is not provided, the random bytes are generated
synchronously and returned as a [`Buffer`][]. An error will be thrown if
there is a problem generating the bytes.

```mjs
// Synchronous
const {
  randomBytes
} = await import('crypto');

const buf = randomBytes(256);
console.log(
  `${buf.length} bytes of random data: ${buf.toString('hex')}`);
```

```cjs
// Synchronous
const {
  randomBytes,
} = require('crypto');

const buf = randomBytes(256);
console.log(
  `${buf.length} bytes of random data: ${buf.toString('hex')}`);
```

The `crypto.randomBytes()` method will not complete until there is
sufficient entropy available.
This should normally never take longer than a few milliseconds. The only time
when generating the random bytes may conceivably block for a longer period of
time is right after boot, when the whole system is still low on entropy.

This API uses libuv's threadpool, which can have surprising and
negative performance implications for some applications; see the
[`UV_THREADPOOL_SIZE`][] documentation for more information.

The asynchronous version of `crypto.randomBytes()` is carried out in a single
threadpool request. To minimize threadpool task length variation, partition
large `randomBytes` requests when doing so as part of fulfilling a client
request.

### `crypto.randomFillSync(buffer[, offset][, size])`

<!-- YAML
added:
  - v7.10.0
  - v6.13.0
changes:
  - version: v9.0.0
    pr-url: https://github.com/nodejs/node/pull/15231
    description: The `buffer` argument may be any `TypedArray` or `DataView`.
-->

* `buffer` {ArrayBuffer|Buffer|TypedArray|DataView} Must be supplied. The
  size of the provided `buffer` must not be larger than `2**31 - 1`.
* `offset` {number} **Default:** `0`
* `size` {number} **Default:** `buffer.length - offset`. The `size` must
  not be larger than `2**31 - 1`.
* Returns: {ArrayBuffer|Buffer|TypedArray|DataView} The object passed as
  `buffer` argument.

Synchronous version of [`crypto.randomFill()`][].

```mjs
import { Buffer } from 'buffer';
const { randomFillSync } = await import('crypto');

const buf = Buffer.alloc(10);
console.log(randomFillSync(buf).toString('hex'));

randomFillSync(buf, 5);
console.log(buf.toString('hex'));

// The above is equivalent to the following:
randomFillSync(buf, 5, 5);
console.log(buf.toString('hex'));
```

```cjs
const { randomFillSync } = require('crypto');
const { Buffer } = require('buffer');

const buf = Buffer.alloc(10);
console.log(randomFillSync(buf).toString('hex'));

randomFillSync(buf, 5);
console.log(buf.toString('hex'));

// The above is equivalent to the following:
randomFillSync(buf, 5, 5);
console.log(buf.toString('hex'));
```

Any `ArrayBuffer`, `TypedArray` or `DataView` instance may be passed as
`buffer`.

```mjs
import { Buffer } from 'buffer';
const { randomFillSync } = await import('crypto');

const a = new Uint32Array(10);
console.log(Buffer.from(randomFillSync(a).buffer,
                        a.byteOffset, a.byteLength).toString('hex'));

const b = new DataView(new ArrayBuffer(10));
console.log(Buffer.from(randomFillSync(b).buffer,
                        b.byteOffset, b.byteLength).toString('hex'));

const c = new ArrayBuffer(10);
console.log(Buffer.from(randomFillSync(c)).toString('hex'));
```

```cjs
const { randomFillSync } = require('crypto');
const { Buffer } = require('buffer');

const a = new Uint32Array(10);
console.log(Buffer.from(randomFillSync(a).buffer,
                        a.byteOffset, a.byteLength).toString('hex'));

const b = new DataView(new ArrayBuffer(10));
console.log(Buffer.from(randomFillSync(b).buffer,
                        b.byteOffset, b.byteLength).toString('hex'));

const c = new ArrayBuffer(10);
console.log(Buffer.from(randomFillSync(c)).toString('hex'));
```

### `crypto.randomFill(buffer[, offset][, size], callback)`

<!-- YAML
added:
  - v7.10.0
  - v6.13.0
changes:
  - version: v9.0.0
    pr-url: https://github.com/nodejs/node/pull/15231
    description: The `buffer` argument may be any `TypedArray` or `DataView`.
-->

* `buffer` {ArrayBuffer|Buffer|TypedArray|DataView} Must be supplied. The
  size of the provided `buffer` must not be larger than `2**31 - 1`.
* `offset` {number} **Default:** `0`
* `size` {number} **Default:** `buffer.length - offset`. The `size` must
  not be larger than `2**31 - 1`.
* `callback` {Function} `function(err, buf) {}`.

This function is similar to [`crypto.randomBytes()`][] but requires the first
argument to be a [`Buffer`][] that will be filled. It also
requires that a callback is passed in.

If the `callback` function is not provided, an error will be thrown.

```mjs
import { Buffer } from 'buffer';
const { randomFill } = await import('crypto');

const buf = Buffer.alloc(10);
randomFill(buf, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

randomFill(buf, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

// The above is equivalent to the following:
randomFill(buf, 5, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});
```

```cjs
const { randomFill } = require('crypto');
const { Buffer } = require('buffer');

const buf = Buffer.alloc(10);
randomFill(buf, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

randomFill(buf, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});

// The above is equivalent to the following:
randomFill(buf, 5, 5, (err, buf) => {
  if (err) throw err;
  console.log(buf.toString('hex'));
});
```

Any `ArrayBuffer`, `TypedArray`, or `DataView` instance may be passed as
`buffer`.

While this includes instances of `Float32Array` and `Float64Array`, this
function should not be used to generate random floating-point numbers. The
result may contain `+Infinity`, `-Infinity`, and `NaN`, and even if the array
contains finite numbers only, they are not drawn from a uniform random
distribution and have no meaningful lower or upper bounds.

```mjs
import { Buffer } from 'buffer';
const { randomFill } = await import('crypto');

const a = new Uint32Array(10);
randomFill(a, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
    .toString('hex'));
});

const b = new DataView(new ArrayBuffer(10));
randomFill(b, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
    .toString('hex'));
});

const c = new ArrayBuffer(10);
randomFill(c, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf).toString('hex'));
});
```

```cjs
const { randomFill } = require('crypto');
const { Buffer } = require('buffer');

const a = new Uint32Array(10);
randomFill(a, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
    .toString('hex'));
});

const b = new DataView(new ArrayBuffer(10));
randomFill(b, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf.buffer, buf.byteOffset, buf.byteLength)
    .toString('hex'));
});

const c = new ArrayBuffer(10);
randomFill(c, (err, buf) => {
  if (err) throw err;
  console.log(Buffer.from(buf).toString('hex'));
});
```

This API uses libuv's threadpool, which can have surprising and
negative performance implications for some applications; see the
[`UV_THREADPOOL_SIZE`][] documentation for more information.

The asynchronous version of `crypto.randomFill()` is carried out in a single
threadpool request. To minimize threadpool task length variation, partition
large `randomFill` requests when doing so as part of fulfilling a client
request.

### `crypto.randomInt([min, ]max[, callback])`

<!-- YAML
added:
  - v14.10.0
  - v12.19.0
-->

* `min` {integer} Start of random range (inclusive). **Default:** `0`.
* `max` {integer} End of random range (exclusive).
* `callback` {Function} `function(err, n) {}`.

Return a random integer `n` such that `min <= n < max`.  This
implementation avoids [modulo bias][].

The range (`max - min`) must be less than 2<sup>48</sup>. `min` and `max` must
be [safe integers][].

If the `callback` function is not provided, the random integer is
generated synchronously.

```mjs
// Asynchronous
const {
  randomInt
} = await import('crypto');

randomInt(3, (err, n) => {
  if (err) throw err;
  console.log(`Random number chosen from (0, 1, 2): ${n}`);
});
```

```cjs
// Asynchronous
const {
  randomInt,
} = require('crypto');

randomInt(3, (err, n) => {
  if (err) throw err;
  console.log(`Random number chosen from (0, 1, 2): ${n}`);
});
```

```mjs
// Synchronous
const {
  randomInt
} = await import('crypto');

const n = randomInt(3);
console.log(`Random number chosen from (0, 1, 2): ${n}`);
```

```cjs
// Synchronous
const {
  randomInt,
} = require('crypto');

const n = randomInt(3);
console.log(`Random number chosen from (0, 1, 2): ${n}`);
```

```mjs
// With `min` argument
const {
  randomInt
} = await import('crypto');

const n = randomInt(1, 7);
console.log(`The dice rolled: ${n}`);
```

```cjs
// With `min` argument
const {
  randomInt,
} = require('crypto');

const n = randomInt(1, 7);
console.log(`The dice rolled: ${n}`);
```

### `crypto.randomUUID([options])`

<!-- YAML
added:
  - v15.6.0
  - v14.17.0
-->

* `options` {Object}
  * `disableEntropyCache` {boolean} By default, to improve performance,
    Node.js generates and caches enough
    random data to generate up to 128 random UUIDs. To generate a UUID
    without using the cache, set `disableEntropyCache` to `true`.
    **Default:** `false`.
* Returns: {string}

Generates a random [RFC 4122][] version 4 UUID. The UUID is generated using a
cryptographic pseudorandom number generator.

### `crypto.scrypt(password, salt, keylen[, options], callback)`

<!-- YAML
added: v10.5.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The password and salt arguments can also be ArrayBuffer
                 instances.
  - version:
     - v12.8.0
     - v10.17.0
    pr-url: https://github.com/nodejs/node/pull/28799
    description: The `maxmem` value can now be any safe integer.
  - version: v10.9.0
    pr-url: https://github.com/nodejs/node/pull/21525
    description: The `cost`, `blockSize` and `parallelization` option names
                 have been added.
-->

* `password` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `salt` {string|ArrayBuffer|Buffer|TypedArray|DataView}
* `keylen` {number}
* `options` {Object}
  * `cost` {number} CPU/memory cost parameter. Must be a power of two greater
    than one. **Default:** `16384`.
  * `blockSize` {number} Block size parameter. **Default:** `8`.
  * `parallelization` {number} Parallelization parameter. **Default:** `1`.
  * `N` {number} Alias for `cost`. Only one of both may be specified.
  * `r` {number} Alias for `blockSize`. Only one of both may be specified.
  * `p` {number} Alias for `parallelization`. Only one of both may be specified.
  * `maxmem` {number} Memory upper bound. It is an error when (approximately)
    `128 * N * r > maxmem`. **Default:** `32 * 1024 * 1024`.
* `callback` {Function}
  * `err` {Error}
  * `derivedKey` {Buffer}

Provides an asynchronous [scrypt][] implementation. Scrypt is a password-based
key derivation function that is designed to be expensive computationally and
memory-wise in order to make brute-force attacks unrewarding.

The `salt` should be as unique as possible. It is recommended that a salt is
random and at least 16 bytes long. See [NIST SP 800-132][] for details.

When passing strings for `password` or `salt`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

The `callback` function is called with two arguments: `err` and `derivedKey`.
`err` is an exception object when key derivation fails, otherwise `err` is
`null`. `derivedKey` is passed to the callback as a [`Buffer`][].

An exception is thrown when any of the input arguments specify invalid values
or types.

```mjs
const {
  scrypt
} = await import('crypto');

// Using the factory defaults.
scrypt('password', 'salt', 64, (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...08d59ae'
});
// Using a custom N parameter. Must be a power of two.
scrypt('password', 'salt', 64, { N: 1024 }, (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...aa39b34'
});
```

```cjs
const {
  scrypt,
} = require('crypto');

// Using the factory defaults.
scrypt('password', 'salt', 64, (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...08d59ae'
});
// Using a custom N parameter. Must be a power of two.
scrypt('password', 'salt', 64, { N: 1024 }, (err, derivedKey) => {
  if (err) throw err;
  console.log(derivedKey.toString('hex'));  // '3745e48...aa39b34'
});
```

### `crypto.scryptSync(password, salt, keylen[, options])`

<!-- YAML
added: v10.5.0
changes:
  - version:
     - v12.8.0
     - v10.17.0
    pr-url: https://github.com/nodejs/node/pull/28799
    description: The `maxmem` value can now be any safe integer.
  - version: v10.9.0
    pr-url: https://github.com/nodejs/node/pull/21525
    description: The `cost`, `blockSize` and `parallelization` option names
                 have been added.
-->

* `password` {string|Buffer|TypedArray|DataView}
* `salt` {string|Buffer|TypedArray|DataView}
* `keylen` {number}
* `options` {Object}
  * `cost` {number} CPU/memory cost parameter. Must be a power of two greater
    than one. **Default:** `16384`.
  * `blockSize` {number} Block size parameter. **Default:** `8`.
  * `parallelization` {number} Parallelization parameter. **Default:** `1`.
  * `N` {number} Alias for `cost`. Only one of both may be specified.
  * `r` {number} Alias for `blockSize`. Only one of both may be specified.
  * `p` {number} Alias for `parallelization`. Only one of both may be specified.
  * `maxmem` {number} Memory upper bound. It is an error when (approximately)
    `128 * N * r > maxmem`. **Default:** `32 * 1024 * 1024`.
* Returns: {Buffer}

Provides a synchronous [scrypt][] implementation. Scrypt is a password-based
key derivation function that is designed to be expensive computationally and
memory-wise in order to make brute-force attacks unrewarding.

The `salt` should be as unique as possible. It is recommended that a salt is
random and at least 16 bytes long. See [NIST SP 800-132][] for details.

When passing strings for `password` or `salt`, please consider
[caveats when using strings as inputs to cryptographic APIs][].

An exception is thrown when key derivation fails, otherwise the derived key is
returned as a [`Buffer`][].

An exception is thrown when any of the input arguments specify invalid values
or types.

```mjs
const {
  scryptSync
} = await import('crypto');
// Using the factory defaults.

const key1 = scryptSync('password', 'salt', 64);
console.log(key1.toString('hex'));  // '3745e48...08d59ae'
// Using a custom N parameter. Must be a power of two.
const key2 = scryptSync('password', 'salt', 64, { N: 1024 });
console.log(key2.toString('hex'));  // '3745e48...aa39b34'
```

```cjs
const {
  scryptSync,
} = require('crypto');
// Using the factory defaults.

const key1 = scryptSync('password', 'salt', 64);
console.log(key1.toString('hex'));  // '3745e48...08d59ae'
// Using a custom N parameter. Must be a power of two.
const key2 = scryptSync('password', 'salt', 64, { N: 1024 });
console.log(key2.toString('hex'));  // '3745e48...aa39b34'
```

### `crypto.secureHeapUsed()`

<!-- YAML
added: v15.6.0
-->

* Returns: {Object}
  * `total` {number} The total allocated secure heap size as specified
    using the `--secure-heap=n` command-line flag.
  * `min` {number} The minimum allocation from the secure heap as
    specified using the `--secure-heap-min` command-line flag.
  * `used` {number} The total number of bytes currently allocated from
    the secure heap.
  * `utilization` {number} The calculated ratio of `used` to `total`
    allocated bytes.

### `crypto.setEngine(engine[, flags])`

<!-- YAML
added: v0.11.11
-->

* `engine` {string}
* `flags` {crypto.constants} **Default:** `crypto.constants.ENGINE_METHOD_ALL`

Load and set the `engine` for some or all OpenSSL functions (selected by flags).

`engine` could be either an id or a path to the engine's shared library.

The optional `flags` argument uses `ENGINE_METHOD_ALL` by default. The `flags`
is a bit field taking one of or a mix of the following flags (defined in
`crypto.constants`):

* `crypto.constants.ENGINE_METHOD_RSA`
* `crypto.constants.ENGINE_METHOD_DSA`
* `crypto.constants.ENGINE_METHOD_DH`
* `crypto.constants.ENGINE_METHOD_RAND`
* `crypto.constants.ENGINE_METHOD_EC`
* `crypto.constants.ENGINE_METHOD_CIPHERS`
* `crypto.constants.ENGINE_METHOD_DIGESTS`
* `crypto.constants.ENGINE_METHOD_PKEY_METHS`
* `crypto.constants.ENGINE_METHOD_PKEY_ASN1_METHS`
* `crypto.constants.ENGINE_METHOD_ALL`
* `crypto.constants.ENGINE_METHOD_NONE`

The flags below are deprecated in OpenSSL-1.1.0.

* `crypto.constants.ENGINE_METHOD_ECDH`
* `crypto.constants.ENGINE_METHOD_ECDSA`
* `crypto.constants.ENGINE_METHOD_STORE`

### `crypto.setFips(bool)`

<!-- YAML
added: v10.0.0
-->

* `bool` {boolean} `true` to enable FIPS mode.

Enables the FIPS compliant crypto provider in a FIPS-enabled Node.js build.
Throws an error if FIPS mode is not available.

### `crypto.sign(algorithm, data, key[, callback])`

<!-- YAML
added: v12.0.0
changes:
  - version: v15.12.0
    pr-url: https://github.com/nodejs/node/pull/37500
    description: Optional callback argument added.
  - version:
     - v13.2.0
     - v12.16.0
    pr-url: https://github.com/nodejs/node/pull/29292
    description: This function now supports IEEE-P1363 DSA and ECDSA signatures.
-->

<!--lint disable maximum-line-length remark-lint-->

* `algorithm` {string | null | undefined}
* `data` {ArrayBuffer|Buffer|TypedArray|DataView}
* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
* `callback` {Function}
  * `err` {Error}
  * `signature` {Buffer}
* Returns: {Buffer} if the `callback` function is not provided.

<!--lint enable maximum-line-length remark-lint-->

Calculates and returns the signature for `data` using the given private key and
algorithm. If `algorithm` is `null` or `undefined`, then the algorithm is
dependent upon the key type (especially Ed25519 and Ed448).

If `key` is not a [`KeyObject`][], this function behaves as if `key` had been
passed to [`crypto.createPrivateKey()`][]. If it is an object, the following
additional properties can be passed:

* `dsaEncoding` {string} For DSA and ECDSA, this option specifies the
  format of the generated signature. It can be one of the following:
  * `'der'` (default): DER-encoded ASN.1 signature structure encoding `(r, s)`.
  * `'ieee-p1363'`: Signature format `r || s` as proposed in IEEE-P1363.
* `padding` {integer} Optional padding value for RSA, one of the following:

  * `crypto.constants.RSA_PKCS1_PADDING` (default)
  * `crypto.constants.RSA_PKCS1_PSS_PADDING`

  `RSA_PKCS1_PSS_PADDING` will use MGF1 with the same hash function
  used to sign the message as specified in section 3.1 of [RFC 4055][].
* `saltLength` {integer} Salt length for when padding is
  `RSA_PKCS1_PSS_PADDING`. The special value
  `crypto.constants.RSA_PSS_SALTLEN_DIGEST` sets the salt length to the digest
  size, `crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN` (default) sets it to the
  maximum permissible value.

If the `callback` function is provided this function uses libuv's threadpool.

### `crypto.subtle`

<!-- YAML
added: v17.4.0
-->

* Type: {SubtleCrypto}

A convenient alias for [`crypto.webcrypto.subtle`][].

### `crypto.timingSafeEqual(a, b)`

<!-- YAML
added: v6.6.0
changes:
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The a and b arguments can also be ArrayBuffer.
-->

* `a` {ArrayBuffer|Buffer|TypedArray|DataView}
* `b` {ArrayBuffer|Buffer|TypedArray|DataView}
* Returns: {boolean}

This function is based on a constant-time algorithm.
Returns true if `a` is equal to `b`, without leaking timing information that
would allow an attacker to guess one of the values. This is suitable for
comparing HMAC digests or secret values like authentication cookies or
[capability urls](https://www.w3.org/TR/capability-urls/).

`a` and `b` must both be `Buffer`s, `TypedArray`s, or `DataView`s, and they
must have the same byte length. An error is thrown if `a` and `b` have
different byte lengths.

If at least one of `a` and `b` is a `TypedArray` with more than one byte per
entry, such as `Uint16Array`, the result will be computed using the platform
byte order.

Use of `crypto.timingSafeEqual` does not guarantee that the _surrounding_ code
is timing-safe. Care should be taken to ensure that the surrounding code does
not introduce timing vulnerabilities.

### `crypto.verify(algorithm, data, key, signature[, callback])`

<!-- YAML
added: v12.0.0
changes:
  - version: v15.12.0
    pr-url: https://github.com/nodejs/node/pull/37500
    description: Optional callback argument added.
  - version: v15.0.0
    pr-url: https://github.com/nodejs/node/pull/35093
    description: The data, key, and signature arguments can also be ArrayBuffer.
  - version:
     - v13.2.0
     - v12.16.0
    pr-url: https://github.com/nodejs/node/pull/29292
    description: This function now supports IEEE-P1363 DSA and ECDSA signatures.
-->

<!--lint disable maximum-line-length remark-lint-->

* `algorithm` {string|null|undefined}
* `data` {ArrayBuffer| Buffer|TypedArray|DataView}
* `key` {Object|string|ArrayBuffer|Buffer|TypedArray|DataView|KeyObject|CryptoKey}
* `signature` {ArrayBuffer|Buffer|TypedArray|DataView}
* `callback` {Function}
  * `err` {Error}
  * `result` {boolean}
* Returns: {boolean} `true` or `false` depending on the validity of the
  signature for the data and public key if the `callback` function is not
  provided.

<!--lint enable maximum-line-length remark-lint-->

Verifies the given signature for `data` using the given key and algorithm. If
`algorithm` is `null` or `undefined`, then the algorithm is dependent upon the
key type (especially Ed25519 and Ed448).

If `key` is not a [`KeyObject`][], this function behaves as if `key` had been
passed to [`crypto.createPublicKey()`][]. If it is an object, the following
additional properties can be passed:

* `dsaEncoding` {string} For DSA and ECDSA, this option specifies the
  format of the signature. It can be one of the following:
  * `'der'` (default): DER-encoded ASN.1 signature structure encoding `(r, s)`.
  * `'ieee-p1363'`: Signature format `r || s` as proposed in IEEE-P1363.
* `padding` {integer} Optional padding value for RSA, one of the following:

  * `crypto.constants.RSA_PKCS1_PADDING` (default)
  * `crypto.constants.RSA_PKCS1_PSS_PADDING`

  `RSA_PKCS1_PSS_PADDING` will use MGF1 with the same hash function
  used to sign the message as specified in section 3.1 of [RFC 4055][].
* `saltLength` {integer} Salt length for when padding is
  `RSA_PKCS1_PSS_PADDING`. The special value
  `crypto.constants.RSA_PSS_SALTLEN_DIGEST` sets the salt length to the digest
  size, `crypto.constants.RSA_PSS_SALTLEN_MAX_SIGN` (default) sets it to the
  maximum permissible value.

The `signature` argument is the previously calculated signature for the `data`.

Because public keys can be derived from private keys, a private key or a public
key may be passed for `key`.

If the `callback` function is provided this function uses libuv's threadpool.

### `crypto.webcrypto`

<!-- YAML
added: v15.0.0
-->

Type: {Crypto} An implementation of the Web Crypto API standard.

See the [Web Crypto API documentation][] for details.

## Notes

### Using strings as inputs to cryptographic APIs

For historical reasons, many cryptographic APIs provided by Node.js accept
strings as inputs where the underlying cryptographic algorithm works on byte
sequences. These instances include plaintexts, ciphertexts, symmetric keys,
initialization vectors, passphrases, salts, authentication tags,
and additional authenticated data.

When passing strings to cryptographic APIs, consider the following factors.

* Not all byte sequences are valid UTF-8 strings. Therefore, when a byte
  sequence of length `n` is derived from a string, its entropy is generally
  lower than the entropy of a random or pseudorandom `n` byte sequence.
  For example, no UTF-8 string will result in the byte sequence `c0 af`. Secret
  keys should almost exclusively be random or pseudorandom byte sequences.
* Similarly, when converting random or pseudorandom byte sequences to UTF-8
  strings, subsequences that do not represent valid code points may be replaced
  by the Unicode replacement character (`U+FFFD`). The byte representation of
  the resulting Unicode string may, therefore, not be equal to the byte sequence
  that the string was created from.

  ```js
  const original = [0xc0, 0xaf];
  const bytesAsString = Buffer.from(original).toString('utf8');
  const stringAsBytes = Buffer.from(bytesAsString, 'utf8');
  console.log(stringAsBytes);
  // Prints '<Buffer ef bf bd ef bf bd>'.
  ```

  The outputs of ciphers, hash functions, signature algorithms, and key
  derivation functions are pseudorandom byte sequences and should not be
  used as Unicode strings.
* When strings are obtained from user input, some Unicode characters can be
  represented in multiple equivalent ways that result in different byte
  sequences. For example, when passing a user passphrase to a key derivation
  function, such as PBKDF2 or scrypt, the result of the key derivation function
  depends on whether the string uses composed or decomposed characters. Node.js
  does not normalize character representations. Developers should consider using
  [`String.prototype.normalize()`][] on user inputs before passing them to
  cryptographic APIs.

### Legacy streams API (prior to Node.js 0.10)

The Crypto module was added to Node.js before there was the concept of a
unified Stream API, and before there were [`Buffer`][] objects for handling
binary data. As such, the many of the `crypto` defined classes have methods not
typically found on other Node.js classes that implement the [streams][stream]
API (e.g. `update()`, `final()`, or `digest()`). Also, many methods accepted
and returned `'latin1'` encoded strings by default rather than `Buffer`s. This
default was changed after Node.js v0.8 to use [`Buffer`][] objects by default
instead.

### Support for weak or compromised algorithms

The `crypto` module still supports some algorithms which are already
compromised and are not currently recommended for use. The API also allows
the use of ciphers and hashes with a small key size that are too weak for safe
use.

Users should take full responsibility for selecting the crypto
algorithm and key size according to their security requirements.

Based on the recommendations of [NIST SP 800-131A][]:

* MD5 and SHA-1 are no longer acceptable where collision resistance is
  required such as digital signatures.
* The key used with RSA, DSA, and DH algorithms is recommended to have
  at least 2048 bits and that of the curve of ECDSA and ECDH at least
  224 bits, to be safe to use for several years.
* The DH groups of `modp1`, `modp2` and `modp5` have a key size
  smaller than 2048 bits and are not recommended.

See the reference for other recommendations and details.

Some algorithms that have known weaknesses and are of little relevance in
practice are only available through the [legacy provider][], which is not
enabled by default.

### CCM mode

CCM is one of the supported [AEAD algorithms][]. Applications which use this
mode must adhere to certain restrictions when using the cipher API:

* The authentication tag length must be specified during cipher creation by
  setting the `authTagLength` option and must be one of 4, 6, 8, 10, 12, 14 or
  16 bytes.
* The length of the initialization vector (nonce) `N` must be between 7 and 13
  bytes (`7 ≤ N ≤ 13`).
* The length of the plaintext is limited to `2 ** (8 * (15 - N))` bytes.
* When decrypting, the authentication tag must be set via `setAuthTag()` before
  calling `update()`.
  Otherwise, decryption will fail and `final()` will throw an error in
  compliance with section 2.6 of [RFC 3610][].
* Using stream methods such as `write(data)`, `end(data)` or `pipe()` in CCM
  mode might fail as CCM cannot handle more than one chunk of data per instance.
* When passing additional authenticated data (AAD), the length of the actual
  message in bytes must be passed to `setAAD()` via the `plaintextLength`
  option.
  Many crypto libraries include the authentication tag in the ciphertext,
  which means that they produce ciphertexts of the length
  `plaintextLength + authTagLength`. Node.js does not include the authentication
  tag, so the ciphertext length is always `plaintextLength`.
  This is not necessary if no AAD is used.
* As CCM processes the whole message at once, `update()` must be called exactly
  once.
* Even though calling `update()` is sufficient to encrypt/decrypt the message,
  applications _must_ call `final()` to compute or verify the
  authentication tag.

```mjs
import { Buffer } from 'buffer';
const {
  createCipheriv,
  createDecipheriv,
  randomBytes
} = await import('crypto');

const key = 'keykeykeykeykeykeykeykey';
const nonce = randomBytes(12);

const aad = Buffer.from('0123456789', 'hex');

const cipher = createCipheriv('aes-192-ccm', key, nonce, {
  authTagLength: 16
});
const plaintext = 'Hello world';
cipher.setAAD(aad, {
  plaintextLength: Buffer.byteLength(plaintext)
});
const ciphertext = cipher.update(plaintext, 'utf8');
cipher.final();
const tag = cipher.getAuthTag();

// Now transmit { ciphertext, nonce, tag }.

const decipher = createDecipheriv('aes-192-ccm', key, nonce, {
  authTagLength: 16
});
decipher.setAuthTag(tag);
decipher.setAAD(aad, {
  plaintextLength: ciphertext.length
});
const receivedPlaintext = decipher.update(ciphertext, null, 'utf8');

try {
  decipher.final();
} catch (err) {
  throw new Error('Authentication failed!', { cause: err });
}

console.log(receivedPlaintext);
```

```cjs
const {
  createCipheriv,
  createDecipheriv,
  randomBytes,
} = require('crypto');
const { Buffer } = require('buffer');

const key = 'keykeykeykeykeykeykeykey';
const nonce = randomBytes(12);

const aad = Buffer.from('0123456789', 'hex');

const cipher = createCipheriv('aes-192-ccm', key, nonce, {
  authTagLength: 16
});
const plaintext = 'Hello world';
cipher.setAAD(aad, {
  plaintextLength: Buffer.byteLength(plaintext)
});
const ciphertext = cipher.update(plaintext, 'utf8');
cipher.final();
const tag = cipher.getAuthTag();

// Now transmit { ciphertext, nonce, tag }.

const decipher = createDecipheriv('aes-192-ccm', key, nonce, {
  authTagLength: 16
});
decipher.setAuthTag(tag);
decipher.setAAD(aad, {
  plaintextLength: ciphertext.length
});
const receivedPlaintext = decipher.update(ciphertext, null, 'utf8');

try {
  decipher.final();
} catch (err) {
  throw new Error('Authentication failed!', { cause: err });
}

console.log(receivedPlaintext);
```

## Crypto constants

The following constants exported by `crypto.constants` apply to various uses of
the `crypto`, `tls`, and `https` modules and are generally specific to OpenSSL.

### OpenSSL options

See the [list of SSL OP Flags][] for details.

<table>
  <tr>
    <th>Constant</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>SSL_OP_ALL</code></td>
    <td>Applies multiple bug workarounds within OpenSSL. See
    <a href="https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html">https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html</a>
    for detail.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_ALLOW_NO_DHE_KEX</code></td>
    <td>Instructs OpenSSL to allow a non-[EC]DHE-based key exchange mode
    for TLS v1.3</td>
  </tr>
  <tr>
    <td><code>SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION</code></td>
    <td>Allows legacy insecure renegotiation between OpenSSL and unpatched
    clients or servers. See
    <a href="https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html">https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html</a>.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_CIPHER_SERVER_PREFERENCE</code></td>
    <td>Attempts to use the server's preferences instead of the client's when
    selecting a cipher. Behavior depends on protocol version. See
    <a href="https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html">https://www.openssl.org/docs/man1.0.2/ssl/SSL_CTX_set_options.html</a>.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_CISCO_ANYCONNECT</code></td>
    <td>Instructs OpenSSL to use Cisco's "speshul" version of DTLS_BAD_VER.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_COOKIE_EXCHANGE</code></td>
    <td>Instructs OpenSSL to turn on cookie exchange.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_CRYPTOPRO_TLSEXT_BUG</code></td>
    <td>Instructs OpenSSL to add server-hello extension from an early version
    of the cryptopro draft.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS</code></td>
    <td>Instructs OpenSSL to disable a SSL 3.0/TLS 1.0 vulnerability
    workaround added in OpenSSL 0.9.6d.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_EPHEMERAL_RSA</code></td>
    <td>Instructs OpenSSL to always use the tmp_rsa key when performing RSA
    operations.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_LEGACY_SERVER_CONNECT</code></td>
    <td>Allows initial connection to servers that do not support RI.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_MICROSOFT_SESS_ID_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_MSIE_SSLV2_RSA_PADDING</code></td>
    <td>Instructs OpenSSL to disable the workaround for a man-in-the-middle
    protocol-version vulnerability in the SSL 2.0 server implementation.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NETSCAPE_CA_DN_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_NETSCAPE_CHALLENGE_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_NETSCAPE_DEMO_CIPHER_CHANGE_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_COMPRESSION</code></td>
    <td>Instructs OpenSSL to disable support for SSL/TLS compression.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_ENCRYPT_THEN_MAC</code></td>
    <td>Instructs OpenSSL to disable encrypt-then-MAC.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_QUERY_MTU</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_RENEGOTIATION</code></td>
    <td>Instructs OpenSSL to disable renegotiation.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION</code></td>
    <td>Instructs OpenSSL to always start a new session when performing
    renegotiation.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_SSLv2</code></td>
    <td>Instructs OpenSSL to turn off SSL v2</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_SSLv3</code></td>
    <td>Instructs OpenSSL to turn off SSL v3</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_TICKET</code></td>
    <td>Instructs OpenSSL to disable use of RFC4507bis tickets.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_TLSv1</code></td>
    <td>Instructs OpenSSL to turn off TLS v1</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_TLSv1_1</code></td>
    <td>Instructs OpenSSL to turn off TLS v1.1</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_TLSv1_2</code></td>
    <td>Instructs OpenSSL to turn off TLS v1.2</td>
  </tr>
  <tr>
    <td><code>SSL_OP_NO_TLSv1_3</code></td>
    <td>Instructs OpenSSL to turn off TLS v1.3</td>
  </tr>
  <tr>
    <td><code>SSL_OP_PKCS1_CHECK_1</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_PKCS1_CHECK_2</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_PRIORITIZE_CHACHA</code></td>
    <td>Instructs OpenSSL server to prioritize ChaCha20Poly1305
    when client does.
    This option has no effect if
    <code>SSL_OP_CIPHER_SERVER_PREFERENCE</code>
    is not enabled.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_SINGLE_DH_USE</code></td>
    <td>Instructs OpenSSL to always create a new key when using
    temporary/ephemeral DH parameters.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_SINGLE_ECDH_USE</code></td>
    <td>Instructs OpenSSL to always create a new key when using
    temporary/ephemeral ECDH parameters.</td>
  </tr>
  <tr>
    <td><code>SSL_OP_SSLEAY_080_CLIENT_DH_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_TLS_BLOCK_PADDING_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_TLS_D5_BUG</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>SSL_OP_TLS_ROLLBACK_BUG</code></td>
    <td>Instructs OpenSSL to disable version rollback attack detection.</td>
  </tr>
</table>

### OpenSSL engine constants

<table>
  <tr>
    <th>Constant</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_RSA</code></td>
    <td>Limit engine usage to RSA</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_DSA</code></td>
    <td>Limit engine usage to DSA</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_DH</code></td>
    <td>Limit engine usage to DH</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_RAND</code></td>
    <td>Limit engine usage to RAND</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_EC</code></td>
    <td>Limit engine usage to EC</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_CIPHERS</code></td>
    <td>Limit engine usage to CIPHERS</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_DIGESTS</code></td>
    <td>Limit engine usage to DIGESTS</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_PKEY_METHS</code></td>
    <td>Limit engine usage to PKEY_METHDS</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_PKEY_ASN1_METHS</code></td>
    <td>Limit engine usage to PKEY_ASN1_METHS</td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_ALL</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>ENGINE_METHOD_NONE</code></td>
    <td></td>
  </tr>
</table>

### Other OpenSSL constants

<table>
  <tr>
    <th>Constant</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>DH_CHECK_P_NOT_SAFE_PRIME</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>DH_CHECK_P_NOT_PRIME</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>DH_UNABLE_TO_CHECK_GENERATOR</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>DH_NOT_SUITABLE_GENERATOR</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>ALPN_ENABLED</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_PKCS1_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_SSLV23_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_NO_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_PKCS1_OAEP_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_X931_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_PKCS1_PSS_PADDING</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>RSA_PSS_SALTLEN_DIGEST</code></td>
    <td>Sets the salt length for <code>RSA_PKCS1_PSS_PADDING</code> to the
        digest size when signing or verifying.</td>
  </tr>
  <tr>
    <td><code>RSA_PSS_SALTLEN_MAX_SIGN</code></td>
    <td>Sets the salt length for <code>RSA_PKCS1_PSS_PADDING</code> to the
        maximum permissible value when signing data.</td>
  </tr>
  <tr>
    <td><code>RSA_PSS_SALTLEN_AUTO</code></td>
    <td>Causes the salt length for <code>RSA_PKCS1_PSS_PADDING</code> to be
        determined automatically when verifying a signature.</td>
  </tr>
  <tr>
    <td><code>POINT_CONVERSION_COMPRESSED</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>POINT_CONVERSION_UNCOMPRESSED</code></td>
    <td></td>
  </tr>
  <tr>
    <td><code>POINT_CONVERSION_HYBRID</code></td>
    <td></td>
  </tr>
</table>

### Node.js crypto constants

<table>
  <tr>
    <th>Constant</th>
    <th>Description</th>
  </tr>
  <tr>
    <td><code>defaultCoreCipherList</code></td>
    <td>Specifies the built-in default cipher list used by Node.js.</td>
  </tr>
  <tr>
    <td><code>defaultCipherList</code></td>
    <td>Specifies the active default cipher list used by the current Node.js
    process.</td>
  </tr>
</table>

[AEAD algorithms]: https://en.wikipedia.org/wiki/Authenticated_encryption
[CCM mode]: #ccm-mode
[CVE-2021-44532]: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-44532
[Caveats]: #support-for-weak-or-compromised-algorithms
[Crypto constants]: #crypto-constants
[HTML 5.2]: https://www.w3.org/TR/html52/changes.html#features-removed
[HTML5's `keygen` element]: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/keygen
[JWK]: https://tools.ietf.org/html/rfc7517
[NIST SP 800-131A]: https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.800-131Ar1.pdf
[NIST SP 800-132]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf
[NIST SP 800-38D]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
[Nonce-Disrespecting Adversaries]: https://github.com/nonce-disrespect/nonce-disrespect
[OpenSSL's SPKAC implementation]: https://www.openssl.org/docs/man1.1.0/apps/openssl-spkac.html
[RFC 1421]: https://www.rfc-editor.org/rfc/rfc1421.txt
[RFC 2412]: https://www.rfc-editor.org/rfc/rfc2412.txt
[RFC 2818]: https://www.rfc-editor.org/rfc/rfc2818.txt
[RFC 3526]: https://www.rfc-editor.org/rfc/rfc3526.txt
[RFC 3610]: https://www.rfc-editor.org/rfc/rfc3610.txt
[RFC 4055]: https://www.rfc-editor.org/rfc/rfc4055.txt
[RFC 4122]: https://www.rfc-editor.org/rfc/rfc4122.txt
[RFC 5208]: https://www.rfc-editor.org/rfc/rfc5208.txt
[RFC 5280]: https://www.rfc-editor.org/rfc/rfc5280.txt
[Web Crypto API documentation]: webcrypto.md
[`BN_is_prime_ex`]: https://www.openssl.org/docs/man1.1.1/man3/BN_is_prime_ex.html
[`Buffer`]: buffer.md
[`EVP_BytesToKey`]: https://www.openssl.org/docs/man1.1.0/crypto/EVP_BytesToKey.html
[`KeyObject`]: #class-keyobject
[`Sign`]: #class-sign
[`String.prototype.normalize()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/normalize
[`UV_THREADPOOL_SIZE`]: cli.md#uv_threadpool_sizesize
[`Verify`]: #class-verify
[`cipher.final()`]: #cipherfinaloutputencoding
[`cipher.update()`]: #cipherupdatedata-inputencoding-outputencoding
[`crypto.createCipher()`]: #cryptocreatecipheralgorithm-password-options
[`crypto.createCipheriv()`]: #cryptocreatecipherivalgorithm-key-iv-options
[`crypto.createDecipher()`]: #cryptocreatedecipheralgorithm-password-options
[`crypto.createDecipheriv()`]: #cryptocreatedecipherivalgorithm-key-iv-options
[`crypto.createDiffieHellman()`]: #cryptocreatediffiehellmanprime-primeencoding-generator-generatorencoding
[`crypto.createECDH()`]: #cryptocreateecdhcurvename
[`crypto.createHash()`]: #cryptocreatehashalgorithm-options
[`crypto.createHmac()`]: #cryptocreatehmacalgorithm-key-options
[`crypto.createPrivateKey()`]: #cryptocreateprivatekeykey
[`crypto.createPublicKey()`]: #cryptocreatepublickeykey
[`crypto.createSecretKey()`]: #cryptocreatesecretkeykey-encoding
[`crypto.createSign()`]: #cryptocreatesignalgorithm-options
[`crypto.createVerify()`]: #cryptocreateverifyalgorithm-options
[`crypto.getCurves()`]: #cryptogetcurves
[`crypto.getDiffieHellman()`]: #cryptogetdiffiehellmangroupname
[`crypto.getHashes()`]: #cryptogethashes
[`crypto.privateDecrypt()`]: #cryptoprivatedecryptprivatekey-buffer
[`crypto.privateEncrypt()`]: #cryptoprivateencryptprivatekey-buffer
[`crypto.publicDecrypt()`]: #cryptopublicdecryptkey-buffer
[`crypto.publicEncrypt()`]: #cryptopublicencryptkey-buffer
[`crypto.randomBytes()`]: #cryptorandombytessize-callback
[`crypto.randomFill()`]: #cryptorandomfillbuffer-offset-size-callback
[`crypto.scrypt()`]: #cryptoscryptpassword-salt-keylen-options-callback
[`crypto.webcrypto.getRandomValues()`]: webcrypto.md#cryptogetrandomvaluestypedarray
[`crypto.webcrypto.subtle`]: webcrypto.md#class-subtlecrypto
[`decipher.final()`]: #decipherfinaloutputencoding
[`decipher.update()`]: #decipherupdatedata-inputencoding-outputencoding
[`diffieHellman.setPublicKey()`]: #diffiehellmansetpublickeypublickey-encoding
[`ecdh.generateKeys()`]: #ecdhgeneratekeysencoding-format
[`ecdh.setPrivateKey()`]: #ecdhsetprivatekeyprivatekey-encoding
[`hash.digest()`]: #hashdigestencoding
[`hash.update()`]: #hashupdatedata-inputencoding
[`hmac.digest()`]: #hmacdigestencoding
[`hmac.update()`]: #hmacupdatedata-inputencoding
[`keyObject.export()`]: #keyobjectexportoptions
[`postMessage()`]: worker_threads.md#portpostmessagevalue-transferlist
[`sign.sign()`]: #signsignprivatekey-outputencoding
[`sign.update()`]: #signupdatedata-inputencoding
[`stream.Writable` options]: stream.md#new-streamwritableoptions
[`stream.transform` options]: stream.md#new-streamtransformoptions
[`util.promisify()`]: util.md#utilpromisifyoriginal
[`verify.update()`]: #verifyupdatedata-inputencoding
[`verify.verify()`]: #verifyverifyobject-signature-signatureencoding
[caveats when using strings as inputs to cryptographic APIs]: #using-strings-as-inputs-to-cryptographic-apis
[certificate object]: tls.md#certificate-object
[encoding]: buffer.md#buffers-and-character-encodings
[initialization vector]: https://en.wikipedia.org/wiki/Initialization_vector
[legacy provider]: cli.md#--openssl-legacy-provider
[list of SSL OP Flags]: https://wiki.openssl.org/index.php/List_of_SSL_OP_Flags#Table_of_Options
[modulo bias]: https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#Modulo_bias
[safe integers]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/isSafeInteger
[scrypt]: https://en.wikipedia.org/wiki/Scrypt
[stream]: stream.md
[stream-writable-write]: stream.md#writablewritechunk-encoding-callback