10.7 zk-Bridge

BitNet’s zk-Bridge architecture adds a privacy-preserving layer to cross-chain bridges by integrating zk-SNARKs. Users can transfer assets without revealing their source, destination, or wallet address.

How It Works

1. Deposit

  • Assets are deposited into a bridge smart contract.

  • A commitment hash is generated and stored: commitment = Hash(secret, recipient, amount)

2. zk-SNARK Proof Generation

  • Off-chain, users generate a proof showing ownership of a valid unspent deposit.

  • The proof hides identity, source chain, and amount.

3. Withdrawal

  • The user submits a zk-proof and nullifier (prevents double-spending).

  • The contract verifies the proof and releases the funds anonymously.

Architecture

  • Acts as middleware, not a full bridge replacement.

  • Compatible with EVM chains using Solidity and Circom-based verifiers.

  • Supports modular integration into existing bridge UI/UX.

Benefits

  • Unlinkable Transfers: Breaks connection between deposit and withdrawal events.

  • DeFi Composability: Can be used with private DEXes, lending protocols, and DAOs.

  • Anonymity Set: Mimics privacy features of full ZK systems like Tornado Cash.

Implementation Challenges

  • zk-proof generation is still compute-intensive.

  • Requires robust, decentralized relayer networks.

  • Complex UX (managing secrets, nullifiers) must be abstracted for users.

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