🔐 Password Verification zkApp (Mina Protocol)

A privacy-preserving password verification zkApp built on Mina Protocol (Devnet).
This project demonstrates how a user can prove knowledge of a correct password using zero-knowledge proofs, without revealing the password or any sensitive data on-chain.

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🚀 Project Overview

Traditional smart contracts require inputs to be public.
This zkApp leverages Mina’s zero-knowledge architecture to allow secure authentication where:

• The password is never revealed
• Only a cryptographic proof is verified on-chain
• Incorrect passwords fail locally before any transaction is sent

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✨ Key Features

• 🔒 Zero-knowledge password verification
• 🧠 Poseidon hashing inside zk circuits
• 🧾 On-chain storage of password hash only
• ⚡ Proof-based verification (no re-execution on-chain)
• 🌐 Deployed and tested on Mina Devnet

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🏗️ Architecture

User (Client)

│

│ Password (private)

▼

Local Proof Generation (prove)

│

│ Zero-Knowledge Proof

▼

Mina Blockchain (verify proof only)

• Client: Generates proofs and signs transactions
• zkApp: Stores password hash and verifies correctness
• Blockchain: Verifies proofs, not raw inputs

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📂 Project Structure

project-root/ │

├── src/

│ ├── PasswordVerifierDevnet.ts

├── scripts/

│ ├── deployDevnetPassword.ts

│ ├── callVerifyPasswordDevnet.ts

│ └── readStatePasswordDevnet.ts

├── package.json

├── tsconfig.json

├──.env

└── README.md

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🧠 Smart Contract Logic

The zkApp stores a Poseidon hash of a password on-chain.

verifyPassword(inputPassword)

1. Reads the stored password hash
2. Hashes the provided password inside the circuit
3. Asserts both hashes are equal
4. Generates a zero-knowledge proof

If the assertion fails:

• Proof generation fails
• Transaction is never sent
• No fees are paid

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🔑 Key Concepts Used

• Zero-Knowledge Proofs
• Poseidon Hashing
• zkApp State
• Private/Public Key Cryptography
• Proof-based Smart Contracts

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🛠️ Setup Instructions

1️⃣ Install dependencies

npm install

2️⃣ Create .env file

FEE_PAYER_KEY=<fee_payer_private_key>
ZKAPP_PRIVATE_KEY=<zkapp_private_key>
ZKAPP_ADDRESS=<zkapp_public_key>

3️⃣ Build the project

npm run build

🚀 Deploy zkApp to Devnet

node build/scripts/deployDevnetPassword.js

Output includes:

• zkApp address

• Deployment transaction hash

🔐 Call vertifyPassword

node build/scripts/callVerifyPasswordDevnet.js

• ✅ Correct password → transaction succeeds

• ❌ Wrong password → proof fails locally

📖 Read on-chain State

node build/scripts/readStatePasswordDevnet.js

This reads:

The Poseidon hash of the password stored on-chain

🛠 Tech Stack

Mina Protocol (Devnet)

o1js

TypeScript

Node.js

🔐 Security & Privacy

Password is never stored or revealed

Only the Poseidon hash exists on-chain

Proofs ensure correctness without disclosure

Invalid attempts fail before reaching the blockchain

📜 License

Apache 2.0 License