Protocol architecture

Qietr is built on three open primitives: x402, Groth16 zero-knowledge proofs, and Solana as the settlement layer.

Core architecture

Shielded Pool

Anchor program (Rust)

ZK Circuit

Groth16 over BN254

TypeScript SDK

@qietr/sdk

Relayer

Gasless fee sponsorship

Zero-knowledge circuits

Qietr uses a Groth16 proof system over the BN254 curve with Poseidon hashing. The circuit proves:

Commitment inclusion in the Merkle tree (depth 20)
Nullifier correctness (no double-spends)
Payment amount does not exceed commitment amount
Change commitment correctness

Public signals: [amount, root, nullifierHash, recipient, paymentAmount, changeCommitment]. The amount signal is a Qietr-specific security fix that prevents amount inflation attacks by binding the payment to its denomination tier.

Smart contracts

All three programs are deployed on Solana devnet (unaudited). Upgrade authority: GWxyJs7G9FPUY58UTtUSpVwFuXTRdXzneyBcekxmvuR4.

Program	Program ID (devnet)	Description
qietr-pool	4XH6f74UFTvqx4j9UarXGrRZRrAwbnNNsRFBTfNqmWib	Shielded pool: deposit, withdraw, denomination management
qietr-escrow	DBLjgT9mCjTF3q7zqDCnUrMtHEnBarNwqmk7XojB4FNz	Trust-minimized agent commerce escrow
qietr-msg	6ZAeJCLRrNyMCLYgH5uUdRNbA5usAun94vPtaTM5Xdez	Encrypted on-chain agent messaging

Devnet USDC mint: 4zMMC9srt5Ri5X14GAgXhaHii3GnPAEERYPJgZJDncDU.$QIET CA: MXDRgSQstTKBMunuF2VmcnBejpbidECL5vtCAb6pumpCopied!. Unaudited.

TypeScript SDK

The @qietr/sdk package provides:

QietrSDK — main client class
wrapFetch — transparent x402 payment handling
Note — encrypted note management
MerkleTree — Merkle proof generation
Prover — browser-based ZK proof generation

$ git clone github.com/QietrProtocol/qietr

Build from qietr-sdk/. The npm package @qietr/sdk is not published yet.

Full SDK reference: github.com/QietrProtocol/qietr