Zswap: zk-SNARK Based Non-Interactive Multi-Asset Swaps

Privacy-oriented cryptocurrencies, like Zcash or Monero, provide fair transaction anonymity and confidentiality, but lack important features compared to fully public systems, Ethereum. Specifically, supporting assets of multiple types providing a mechanism atomically exchange them, which is critical for e.g. decentralized finance (DeFi), challenging in the private setting. By combining insights security properties from SwapCT (PETS 21, an atomic swap system Monero), we present simple zk-SNARKs based scheme, called Zswap, carefully malleable allow merging transactions, while preserving anonymity. Our protocol enables exchanges by making use sparse homomorphic commitments with aggregated open randomness, together friendly simulation-extractable non-interactive zero-knowledge (NIZK) proofs. This results provably secure privacypreserving protocol, efficient swaps, overall performance close that existing deployed cryptocurrencies. It similar Sapling benefits code-bases implementation expertise.