🧾 Age Verification zkApp (Mina Devnet)

A privacy-preserving zero-knowledge smart contract built using o1js that verifies whether a user’s age is above a required threshold (e.g., 18) without revealing the actual age.

This zkApp is deployed and tested on Mina Devnet.

---

🚀 Features

• Zero-Knowledge age verification
• Private input: age
• Public rule: age ≥ minAge
• Stores last verified age on-chain (as a Field)

🧠 How It Works (High-Level)

1. The zkApp exposes a method verifyAge(age, minAge)

2. A zero-knowledge proof ensures:

    age ≥ minAge
   

3. If valid, zkApp stores the verified age on-chain

   The verifier checks the proof, without seeing the actual age.

4. Anyone can read the stored value from the blockchain

   This showcases how Mina zkApps can be used for privacy-preserving identity checks.

🔑 Key Roles

Key	Purpose
Fee Payer	Pays transaction fees (MINA)
zkApp Key	Owns and authorizes the zkApp

🗂 Project Structure

project-root/ │

├── src/

│ ├── AgeVerifierDevnet.ts # zkApp smart contract

├── scripts/

│ ├── deployDevnet.ts

│ ├── callVerifyAgeDevnet.ts

│ └── readStateDevnet.ts

│

├── package.json

├── tsconfig.json

└── README.md

---

🌐 Network Configuration

• Network: Mina Devnet
• GraphQL Endpoint:

https://api.minascan.io/node/devnet/v1/graphql

🔍 View on Explorer

https://minascan.io/devnet/account/<ZKAPP_ADDRESS>

📦 Installation

Requires Node.js 18.14.0 or higher.

npm install

🔧 Build the project

npm run build

🚀 Deploy zkApp to Devnet

node build/scripts/deployDevnet.js

After deployment, note:

zkApp address

Transaction hash (from explorer)

Call vertifyAge

node build/scripts/callVerifyAgeDevnet.js

This

• Generates a zk proof

• Calls verifyAge(age, minAge)

• Updates on-chain state

📖 Read on-chain State

node build/scripts/readStateDevnet.js

This reads:

zkApp balance

lastVerified age

🛠 Tech Stack

Mina Protocol (Devnet)

o1js

TypeScript

Node.js

🎯Learning Outcomes

zkApp lifecycle (compile → deploy → call → read)

Fee payer vs zkApp key separation

Devnet transactions

On-chain state management

Zero-knowledge constraints

📜 License

Apache 2.0 License