A secure, anonymous, and scalable peer-to-peer token exchange system powered by zkSNARK proofs and on-chain withdrawal rights management.

Build a privacy-preserving P2P exchange (e.g., USDT) that protects users from tracking, using zkSNARK-based zero-knowledge proofs and Merkle tree commitments.

The Groth16 zkSNARK scheme ensures:

• The user knows the nullifier and secret for an existing commitment
• The note has not been used (nullifierHash unused)
• The note belongs to the current Merkle root
• The recipient can be chosen freely

👉 All without revealing the nullifier, secret, amount, or sender.

• User generates a note {nullifier, secret}
• Creates a commitment: Poseidon(nullifier, secret)
• Calls P2PManager.deposit(commitment, amount)
• Commitment is added to Merkle tree and tokens deposited
• 📝 Note saved in JSON, shareable via private channel

• Send the note to a buyer via Session, QR, or messenger
• Buyer pays in fiat, USDT, or another method

requestWithdraw(commitment, recipientAddress)

• Locks withdrawal rights for a recipient
• Includes expiration (expiresAt) for automatic release if unpaid

• Buyer generates Merkle proof + zkSNARK proof

• Calls withdraw() with proof, root, nullifierHash, recipient

• Contract:

  • Verifies proof via verifier.sol
  • Ensures note not spent before
  • Checks reservation (recipient, expiresAt) if set
  • Sends tokens to recipient
  • Marks nullifierHash as spent

cd circuits/
snarkjs groth16 setup mixer.r1cs pot12_final.ptau mixer.zkey
snarkjs zkey export verificationkey mixer.zkey verification_key.json
snarkjs zkey export solidityverifier mixer.zkey verifier.sol

forge script script/Deploy.s.sol --rpc-url http://localhost:8545 --broadcast

ts-node cli/deposit.ts

ts-node cli/requestWithdraw.ts note.json recipient_address

ts-node cli/withdraw.ts note.json

p2p-mixer/
├── contracts/
│   ├── P2PManager.sol
│   └── verifier.sol
├── circuits/
│   └── mixer.circom
├── cli/
│   ├── deposit.ts
│   ├── requestWithdraw.ts
│   └── withdraw.ts
├── notes/
│   └── note_<timestamp>.json
├── test/
│   └── P2P.t.sol
└── README.md

💡 Contributions and ideas are welcome!