Cryptopals Crypto Challenges in C

Solutions to the Cryptopals Crypto Challenges written in C.

Uses CMake and GTest. Developed on Linux.

Build & Test

mkdir build && cd build
cmake ..
make
ctest --output-on-failure

Project structure

├── CMakeLists.txt
├── include/           # headers (.h)
├── src/               # source code (.c)
├── tests/             # tests (.cpp)
└── notes/             # explanations

Challenges

Set 1 — Basics

#	Challenge
1	Hex to Base64
2	Fixed XOR
3	Single-byte XOR cipher
4	Detect single-char XOR
5	Repeating-key XOR
6	Break repeating-key XOR
7	AES in ECB mode
8	Detect AES in ECB

Set 2 — Block Crypto

#	Challenge
9	PKCS#7 padding
10	Implement CBC mode
11	ECB/CBC detection oracle
12	Byte-at-a-time ECB decryption
13	ECB cut-and-paste
14	Byte-at-a-time ECB with prefix
15	PKCS#7 padding validation
16	CBC bitflipping attack

Set 3 — Block & Stream Crypto

#	Challenge
17	The CBC padding oracle
18	Implement CTR mode
19	Break fixed-nonce CTR
20	Break fixed-nonce CTR statistically
21	Implement MT19937 Mersenne Twister
22	Crack MT19937 seed
23	Clone MT19937 from output
24	MT19937 stream cipher