Chameleon - Cross-chain private multi-sig

Aztec
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1

Contact Details

Mail: anotherdevv@gmail.com

Telegram: @Someone_Nevv & @yashgo0018

Summary

Chameleon is a private cross-chain multisig solution that enables users to control assets on public L2s through a privacy-preserving multisig on Aztec. Our bridge connects Aztec testnet to Optimism Sepolia by using a hybrid approach that combines a relayer network with an optimistic verification mechanism. Users can privately create and manage multisig wallets on Aztec with customizable X out of Y signers thresholds, then use these to authorize transactions on Optimism without revealing tany of the signers or voting patterns. This creates powerful use cases for DAOs, treasury management, and organizations wanting privacy while interacting with defi on public networks to tap into their liquidity sources.

Start and End Date

  • Start Date: We have already started work by exploring current token portal solutions and frontend integration using Aztec.js during EthGlobal Trifecta hackathon in the ZK track.
  • Functional Testnet Release: mid June 2025

About You

We are a team of experienced ZK and blockchain developers with backgrounds in protocol design, web3 auditing and cross-chain infrastructure. Our core team has previously built ZK infrastructure and contributed to multiple protocols. In the past we have struggled to find good cross-chain private execution mechanisms that are in production which motivated us to start working on this project.

Details

Cross-Chain Application Demo

Chameleon allows users to create private multisig wallets on Aztec that can control assets and execute transactions on Optimism. Our demo will showcase:

  1. Private Multisig Creation: Users can set up a multisig wallet on Aztec with custom threshold parameters (e.g., 2-of-3, 3-of-5) without revealing the identities of any signers.
  2. Cross-Chain Asset Control: The multisig can interact with smart contracts on Optimism e.g. send, swap different ERC-20 tokens, NFTs.
  3. Private Governance: Signers can vote privately on Aztec without showing their voting patterns or identities, with final defi interactions executed on Optimism.
  4. Signature Aggregation: Multiple signatures are aggregated into a single proof on Aztec, which is then verified on Optimism.

Bridge Design and Rationale

We’ll implement a hybrid bridge with two primary components:

  1. Relayer Network: A decentralized network of relayers will monitor the Aztec chain for multisig execution events and relay them to Optimism. Initially, we’ll operate a trusted relayer for the MVP but will transition to multiple relayers with economic incentives.
  2. Optimistic Verification: To reduce costs and have better UX we’ll implement optimistic verification system inspired by Across Protocol where relayers post bonds and can be challenged if they relay fraudulent information.

For the MVP, our bridge will focus on ERC-20 token transfers and basic contract interactions for major defi protocols on Optimism.

Meeting Requirements

  1. Bridge to L2 Testnet: We’ll connect Aztec testnet to Optimism Sepolia testnet.
  2. Cross-Chain Demo Dapp: Private multisig application with demonstration of cross-chain functionality.
  3. UI for Transaction Execution: We’ll provide a clean interface for creating multisigs, adding signers, proposing transactions, collecting signatures, and execution of proposed txs.
  4. Bridge Design:
  • MVP will use a trusted relayer network with optimistic verification
  • Roadmap includes plans to implement zk-proofs of Optimism state for trustless verification
  • Will integrate with EIP-7702 for account abstraction on Optimism
  1. Flows:
  • Private deposit into Aztec from Optimism (funds are deposited to multisig privately)
  • Private withdrawal from Aztec to Optimism to execute cross-chain intents
  • Public deposits and withdrawals
  1. Gas Fee Management:
  • We’ll sponsor gas fees for users on Aztec through app-sponsored transactions
  • Will implement an FPC (Fee Payment Contract) that accepts any token for fees
  • Gas fees on Optimism will be sponsored via EIP-4337
  1. Edge Cases:
  • Transaction timeouts for automated refunds
  • L2 re-orgs handled via state verification and challenge period

Technical Hurdles

  1. Private Signature Aggregation: Creating efficient ZK proofs for signature verification.
  2. Cross-Chain State Synchronization: State consistency between Aztec and Optimism especially for edge cases, reorgs etc.
  3. Privacy Preservation: Maintaining privacy guarantees when interacting with public L2s, timing attacks etc.
  4. Gas Optimization: Managing gas costs efficiently, especially for complex operations that may require multiple transactions.

User Flow and Journey

  1. Multisig Creation:
  • User creates a private multisig on Aztec, defining threshold and signers
  • Bridge contract registers a corresponding proxy on Optimism
  • User receives confirmation of successful cross-chain setup
  1. Deposit Flow:
  • User initiates deposit from Optimism to Aztec multisig
  • Transaction verified by bridge contracts on Optimism
  • Relayer observes deposit event, submits proof to Aztec
  • Funds appear in private Aztec multisig with privacy preserved
  1. Transaction Execution Flow:
  • Transaction proposal created privately on Aztec
  • Signers submit private signatures on Aztec
  • When threshold reached, signatures aggregated into single proof
  • Relayer observes execution event, submits to Optimism
  • Transaction executed on Optimism via proxy contract
  1. Withdrawal Flow:
  • Multisig initiates withdrawal from Aztec to Optimism
  • Signatures verified privately on Aztec
  • Withdrawal intent published
  • Relayer executes transaction on Optimism
  • Assets transferred to specified address on Optimism

Grant Milestones and Roadmap

Phase 1: MVP Development (Now - June 2025)

Milestone 1: Core Architecture specs & Bridge Design (4 weeks)

  • Development of core Noir & Solidity contracts
  • Create multisig logic on Aztec
  • Cross-chain demo utilizing current token portals to EVM in Aztec sandbox
  • Initial relayer design
  • Deliverable: Working prototype with basic functionality and technical documentation

Milestone 2: Privacy-Preserving Signature Aggregation (4 weeks)

  • Implementing relayer infrastructure
  • Implementing private signature collection
  • Development of proof generation for signature verification
  • Create threshold signature verification system
  • Deliverable: Private signature mechanism with test cases

Milestone 3: Cross-Chain Execution & UI (4 weeks)

  • Integrate bridges between Aztec and Optimism testnets
  • Integration of multisig management and transaction execution in web app UI
  • Gas fees sponsoring on both chains
  • Deliverable: Functional application on testnet with complete user flow

Phase 2: Future Plans (After June, 2025)

Milestone 4: Decentralized Relayer Network

  • Reseach into bond-based incentive system for relayers
  • Challenge mechanism for incorrect relaying
  • Relayer reputation system

Milestone 5: Enhanced Privacy Features

  • ZK proofs for Optimism state verification
  • Developing privacy-preserving transaction metadata

Milestone 6: Mainnet Launch Preparation

  • Security audits and optimizations
  • More extensive testing
  • Documentation and developer resources for additional defi integrations on different EVM networks

Grant Amount Requested

$50,000

Grant Budget Rationale

Allocation of funds:

  • Development Resources (60%): $30,000
    • Noir contract implementation: $10,000
    • Solidity contract implementation: $5,000
    • Frontend development: $5,000
    • Relayer development: $5,000
  • Infrastructure & Testing (25%): $12,500
    • Relayer infrastructure setup: $5,000
    • Testing: $7,500
  • Operational Expenses (15%): $7,500
    • Cryptography research: $5,000
    • Documentation: $2,500