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.