Cross Chain Catalysts Proposal (Deployment Grant): Private P2P Trading with iExchange

Aztec
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Cross Chain Catalysts Proposal (Deployment Grant): Private P2P Trading with iExchange

Contact Details

Summary

We propose integrating privacy-enhanced cross-chain functionality into iExchange, our proven P2P trading platform. This integration will enable private token purchases where buyers can acquire assets on Base and receive them privately on Aztec, protecting buyer identity throughout the trading process.

The solution leverages Substance Labs’ Base-to-Aztec bridge and implements a secret hash mechanism to ensure buyer privacy while maintaining the trusted escrow system on our platform.

Key Innovation: Transforming traditional P2P trading into a privacy-preserving cross-chain experience, where fiat-to-crypto transactions can be completed with enhanced anonymity.

Timeline

  • Start Date: July 1, 2025
  • End Date: September 15, 2025 (11 weeks)
  • Testnet Deployment Target: September 1, 2025

About You

Our team built a P2P trading app supporting multiple L2s (e.g., Base, Arbitrum), processing over 50,000 transactions on testnet. We have now successfully done a beta stealth launch with over 100 users. With expertise in smart contract development, ZK, blockchain architecture, and UX, we’re set to integrate Aztec’s privacy tech universally.

Proven Track Record:

  • Live P2P trading platform with real users and transaction volume
  • Multi-chain deployment experience across major L2s
  • Strong community engagement with active user base
  • Technical expertise in privacy-preserving technologies

Technical Approach

Current iExchange Buy Flow

1. Order Creation (Off-Chain)
   └── Buyer chooses seller's ad and signs buy order message
   └── Includes expiration deadline for order submission
   └── Seller notified of buyer's intent

2. Seller Acceptance (On-Chain)
   └── Seller signs agreement and approves token transfer
   └── Both signatures submitted to smart contract
   └── Contract validates expiration and locks seller's tokens in escrow

3. Buyer Payment
   └── Buyer pays fiat to seller (off-chain)
   └── Buyer submits "mark as paid" transaction
   └── Contract updates order status

4. Seller Release
   └── Seller verifies fiat payment received
   └── Seller calls release function to transfer tokens to buyer
   └── Contract validates payment status and releases escrowed funds

Key Security Features:

  • :white_check_mark: Escrow-based settlements protecting both parties
  • :white_check_mark: Time-locked orders preventing indefinite locks
  • :white_check_mark: On-chain verification of all critical state changes
  • :white_check_mark: Cancellation mechanisms for failed trades

For the full Protocol Specification visit our Whitepaper

Enhanced Privacy Flow: iExchange + Aztec Integration

Our innovation builds upon this proven foundation by adding privacy preservation and cross-chain delivery through Aztec:

Privacy-Enhanced Buy Order Flow

1. Private Order Creation
   └── Buyer generates secret hash, places private order
   └── Seller sees order with secretHash (buyer identity hidden)

2. Private Escrow
   └── Seller escrows tokens with secretHash as release key
   └── No buyer address stored on-chain

3. Private Payment Confirmation
   └── Buyer pays fiat to seller (existing flow)
   └── Relayer submits "paid" transaction (buyer identity protected)

4. Cross-Chain Release
   └── Seller releases via Substance Labs bridge to Aztec
   └── Private intent created with secretHash as recipient

5. Private Claim
   └── Buyer claims tokens on Aztec using secret
   └── Complete privacy preservation achieved

Detailed Technical Flow

1. Private Order Creation

  • Buyer generates secret (client-side) and computes secretHash = hash(secret)
  • Off-chain order placement using secretHash as privacy identifier
  • Seller receives order with secretHash instead of buyer’s address

2. Escrow with Privacy

  • Seller escrows USDC in modified iExchange contract on Base
  • Funds locked with secretHash as the release key
  • No buyer address stored on-chain during escrow phase

3. Private Payment Confirmation

  • Buyer pays fiat to seller (existing iExchange flow)
  • Relayer service submits “mark as paid” transaction using secretHash
  • Buyer identity hidden - transaction submitted by iExchange backend
  • Gas sponsored by relayer to further preserve privacy

4. Cross-Chain Release

  • Seller confirms fiat receipt (off-chain verification)
  • Smart contract initiates ERC-7683 private intent to Substance Labs bridge
  • Private intent created with secretHash as recipient identifier
  • Funds bridged to Aztec with privacy preserved

5. Private Claim on Aztec

  • Buyer connects to Aztec with any wallet
  • Submits private transaction revealing secret to claim funds
  • Aztec contract verifies hash(secret) == secretHash
  • Tokens released to buyer’s Aztec address

Technical Architecture

Smart Contract Modifications

  • Enhanced escrow system supporting secret hash identifiers
  • New markAsPaidWithSecretHash() function for relayer transactions
  • Modified release function integrating with Substance Labs’ ERC-7683 bridge
  • Privacy-preserving state management avoiding on-chain buyer data

Backend Infrastructure

  • Relayer service for privacy-preserving transaction submission
  • Secret management with client-side generation and storage

Frontend Integration

  • Minimal UI modifications to existing iExchange interface
  • Secret generation and management interface
  • Privacy indicators showing enhanced anonymity features
  • Aztec integration guidance for token claiming

Key Benefits

For Users

  • Enhanced Privacy: Buyer addresses hidden during trading
  • Familiar Experience: Builds on proven iExchange UX
  • Cross-Chain Utility: Receive tokens on privacy-focused Aztec

For Ecosystem

  • Real-World Privacy Application: Practical use case for Aztec
  • Bridge Utilization: Drives adoption of Substance Labs’ infrastructure
  • Proven Platform: Integration with platform that has processed over 40k Testnet transactions with over 100 active mainnet users
  • User Acquisition: Existing user base can onboard to Aztec

Grant Amount Requested: $5,000

Budget Rationale

Smart Contract Development (30% - $1,500)

  • Modify existing iExchange contracts for secret hash support
  • Integrate with Substance Labs’ ERC-7683 bridge interface
  • Implement privacy-preserving escrow mechanisms
  • Testing and security reviews

Backend Infrastructure (30% - $1,000)

  • Develop relayer service for privacy-preserving transactions
  • Secret management and encryption systems
  • API integration with existing iExchange backend

Frontend Integration (40% - $2000)

  • Modify existing UI for private order flows
  • Implement secret generation interface
  • User experience testing and refinement

Testing & Deployment (10% - $500)

  • Comprehensive testnet deployment
  • End-to-end flow testing

Implementation Milestones

Phase 1: Smart Contract Foundation (Weeks 1-4)

  • Week 1-2: Modify iExchange contracts for secret hash support
  • Week 3-4: Integrate Substance Labs bridge, implement ERC-7683 private intents
  • Deliverable: Deployed contracts on Base Testnet

Phase 2: Backend Infrastructure (Weeks 5-7)

  • Week 5-6: Develop relayer service and gas sponsorship
  • Week 6-7: Implement secret management systems
  • Deliverable: Functional backend supporting private flows

Phase 3: Frontend & Integration (Weeks 8-10)

  • Week 8: Modify existing iExchange UI for private orders
  • Week 9: Implement secret generation
  • Week 10: End-to-end testing and UX refinement
  • Deliverable: Complete user interface with privacy features

Phase 4: Deployment & Demo (Week 11)

  • Week 11: Deployment, demo preparation, documentation
  • Deliverable: Live demo on Aztec testnet with full documentation

Future Roadmap

Enhanced Privacy Features

  • Wallet-based secret encryption for improved security
  • Advanced privacy indicators showing anonymity levels
  • ZK proofs for secret knowledge eliminating need for secret revelation

Extended Functionality

  • Multi-token support beyond USDC
  • Dispute resolution mechanisms for failed transactions
  • Bridge failure recovery systems with automated refunds

Platform Expansion

  • Multi-L2 support extending to Arbitrum, Optimism
  • Advanced order types with privacy preservation
  • Mobile app integration with privacy features

Demonstration Plan

Live Demo Features

  • Show full private order flow from creation to Aztec claim
  • Demonstrate buyer privacy preservation throughout process
  • Highlight seamless cross-chain asset transfer
  • Side-by-side comparison of traditional vs private trading
  • Show how buyer identity is protected in new flow
  • Highlight integration with existing iExchange platform
  • Show compatibility with Substance Labs’ bridge
  • Demonstrate Aztec token claiming process

Why This Matters for Aztec

Real-World Adoption

  • Existing user base processing over 50k testnet transactions ready to onboard to Aztec
  • Immediate utility for privacy-conscious traders

Bridge Ecosystem Growth

  • Drives adoption of Substance Labs’ infrastructure
  • Showcases practical applications of cross-chain privacy
  • Creates demand for Aztec-based privacy solutions

Privacy Innovation

  • First privacy-enhanced P2P trading platform integration
  • Demonstrates real-world utility of Aztec’s privacy features
  • Sets precedent for other DeFi privacy integrations