hermes
Hermes is a Fusion+ implementation enabling swaps between Stellar and Ethereum.
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About
Hermes is a Fusion+-style cross-chain bridge enabling atomic swaps between Ethereum-compatible chains and Stellar using HTLCs on Stellar, deterministic contract addresses, and a custom EVM deployment. It features bespoke relayer and resolver services that coordinate off-chain verification, guarantee atomicity, and optimize finality. By integrating Stellar’s native capabilities with EVM programmability, Hermes ensures secure, trust-minimized, and deterministic asset movement across both ecosystems without centralized custody.
How it's made
# Hermes - Cross-Chain Atomic Swap Protocol ## Overview Hermes implements a cross-chain atomic swap protocol using Hash Time Locked Contracts (HTLCs) with time-locked escrow contracts on both Ethereum and Stellar chains. The system ensures trustless, atomic exchanges without requiring centralized custody. ## Core Technologies ### Smart Contracts **Ethereum (EVM)**: Solidity contracts built with Foundry framework - `EscrowFactory` deploys source and destination escrow contracts - `EscrowSrc` and `EscrowDst` handle the actual token locking and unlocking - Uses OpenZeppelin's Create2 for deterministic contract addresses **Stellar**: Rust-based Soroban smart contracts - Mirror functionality of EVM contracts but adapted for Stellar's account model - Built using the Stellar SDK and Soroban CLI ### Frontend Stack - React with TypeScript for the user interface - RainbowKit/Wagmi for Ethereum wallet integration - Freighter for Stellar wallet connectivity - Vite for build tooling and development server ## Cross-Chain Coordination The resolver service (`resolver/nevm.ts`) orchestrates the four-step atomic swap process: 1. **Create Source Escrow**: Deploys and funds escrow on the source chain 2. **Create Destination Escrow**: Deploys corresponding escrow on destination chain 3. **Withdraw Destination**: Recipient claims tokens using the secret 4. **Withdraw Source**: Original sender completes the swap using the revealed secret ## Key Technical Innovations ### Deterministic Addresses The system uses deterministic contract deployment to ensure both parties can independently verify escrow addresses before funding, eliminating trust requirements. ### Time-Lock Mechanisms Sophisticated timelock encoding ensures proper sequencing: - Withdrawal windows for legitimate swaps - Cancellation periods for failed swaps - Public withdrawal/cancellation for resolver intervention ### Cross-Chain State Management The resolver maintains state consistency across chains by: - Generating shared secrets for each swap - Coordinating timing to prevent race conditions - Handling edge cases like network delays or failed transactions ## Development & Deployment ### Monorepo Structure - Modular TypeScript packages for shared utilities - Separate build processes for contracts, frontend, and resolver - Docker containerization for easy deployment ### Testing & Verification - Foundry for EVM contract testing - Rust toolchain for Stellar contract validation - Contract verification on Etherscan for transparency ## Notable Implementation Details ### Secret Management ```typescript const secret = random32Bytes(); const hashlock = keccak256(secret); ``` Each swap uses a unique 32-byte secret, with its keccak256 hash serving as the commitment. ### Cross-Chain Token Bridging The system doesn't actually "bridge" tokens but rather enables atomic exchanges of native tokens on each chain, avoiding the complexities and risks of wrapped token approaches. ### Environment Configuration Extensive environment variable configuration supports multiple networks and deployment scenarios, with separate variables for frontend and backend services. ## Architecture Benefits This architecture creates a trustless bridge that leverages the strengths of both Ethereum's programmability and Stellar's efficiency while maintaining security through cryptographic commitments and time-based constraints.