Zarkclaim
Private Bridge b/w ZCash and Starknet using Zclaim
Demo
About
The problem it solves - **Privacy-Preserving Transfers**: Unlike traditional bridges that expose "User A bridged 100 ZEC" on-chain, ZCLAIM uses Zcash's shielded notes and homomorphic value commitments. The bridge verifies validity without learning amounts, true financial privacy across chains. - **Trustless Custody**: No centralized custodian holds your assets. Multiple independent vaults lock ZEC, each posting 150% collateral. If a vault misbehaves, users claim collateral directly. No single point of failure. - **Cryptographic Proof of Locking**: Zero-knowledge proofs (πZKMint/πZKBurn) prove notes exist in Zcash's Merkle tree, are addressed to the correct vault, and have matching value commitments, all without revealing actual values. - **On-Chain Zcash Verification**: The RelaySystem contract maintains Zcash block headers with PoW verification and Sapling commitment roots, enabling trustless verification of Zcash state on Starknet. - **Challenge-Response Security**: Vaults can challenge bad encryption by revealing shared secrets, with malicious users losing deposits. - **Composable Private DeFi**: wZEC on Starknet enables private trading on DEXs, private collateral in lending, and anonymous DAO participation, extending Zcash privacy into DeFi.
How it's made
Challenges we ran into - **Cairo 2.8 Compiler Issues**: The Cairo compiler panicked when enabling multiple modules with cross-dependencies. Fixed by restructuring the module hierarchy, inlining crypto functions, and adding required Default/Copy traits to storage enums. - **Fixed-Size Array Limitations**: Cairo doesn't support 2D array indexing like Rust. The BLAKE2b sigma permutation table had to be reimplemented as an if-else lookup function instead of sigma.at(round).at(index). - **Zcash Cryptography in Cairo**: Zcash uses BLAKE2b-256, Equihash PoW, and SHA256d—none native to Cairo. Pure implementations would be gas-prohibitive. Solution: use circom circuits for heavy crypto off-chain, verify ZK proofs on-chain. - **Storage Constraints**: Cairo contracts can't store dynamic arrays. Created separate MintTransferStorage structs without Array<felt252> fields for persistence. - **Node.js Import Paths**: ES module resolution failed because utils imported ./config.js instead of ../config.js. Simple path fix resolved the CLI crashes. - **RPC Deprecation**: Starknet public RPC endpoints (BlastAPI) became unreliable, requiring migration to Alchemy/Infura with API keys.