ZpCash SDK

Privacy-preserving identity SDK for the hypothetical ZpCash ecosystem. The toolkit mirrors the ideas from @zkterm/zkid and augments them with a Cairo smart contract for immutable proof anchoring on Starknet.

Features

• did:zpcash:xxxx identity generation backed by Ed25519 keypairs
• Password-based encryption (AES-256-GCM + PBKDF2, 200k iterations)
• Deterministic proof messages with short-lived nonces and timestamping
• Built-in utilities to hash proofs and prepare Starknet call data
• Starknet (STARK curve) wallet management for OpenZeppelin or ArgentX flows
• Cairo smart contract (contracts/src/lib.cairo) to store proof hashes on-chain

Installation

npm install @zpcash/sdk
# or
pnpm add @zpcash/sdk

Install dependencies after cloning this workspace with npm install before running TypeScript builds.

Quick Start

import {
  createZpIdentity,
  generateProof,
  hashProof,
  assembleOnChainProof,
  buildStoreProofCalldata,
} from '@zpcash/sdk';

async function main() {
  const password = 'ChangeMe123!';
  const identity = await createZpIdentity(password);

  const proof = await generateProof({
    zpId: identity.zpId,
    password,
    encrypted: identity.encryptedPrivateKey.encrypted,
    salt: identity.encryptedPrivateKey.salt,
    iv: identity.encryptedPrivateKey.iv,
    iterations: identity.encryptedPrivateKey.iterations,
  });

  const proofHash = hashProof(proof);
  const payload = assembleOnChainProof(proof, identity.zpId);
  const calldata = buildStoreProofCalldata(payload);

  console.log('Proof ID (felt):', payload.proofId);
  console.log('Proof hash (hex):', proofHash.hashHex);
  console.log('Starknet calldata:', calldata);
}

main().catch(console.error);

Starknet Wallet Helpers

import { createZpcashWallet, decryptZpcashPrivateKey } from '@zpcash/sdk';

const wallet = await createZpcashWallet('MyWalletPassword', 'openzeppelin');
console.log(wallet.address);

const privateKey = await decryptZpcashPrivateKey(wallet.encryptedPrivateKey, 'MyWalletPassword');

The helpers rely on the starknet library internally and work with both OpenZeppelin and ArgentX class hashes.

Cairo Contract

The Starknet contract is packaged in contracts/ with Scarb metadata:

contracts/
 ├── README.md
 ├── Scarb.toml
 └── src/
     └── lib.cairo

The contract exposes:

• store_proof(proof_id, proof_hash, zp_id)
• get_proof(proof_id)
• verify_proof_exists(proof_id)

See contracts/README.md for compilation and deployment steps.

Building

npm run build

TypeScript sources compile to dist/ with declaration files for downstream projects.

Security Notes

• Private keys are zeroed in memory immediately after encryption/decryption helpers finish.
• PBKDF2 iterations default to 200,000. Override with caution and always prefer values ≥ 100,000.
• Proof messages expire after 10 minutes by default. Adjust ttlSeconds when calling generateProof if necessary.

License

MIT