Project Overview
Meridian Link is a bidirectional token bridge that enables secure, trustless token transfers between Solana and EVM-compatible blockchains including Ethereum L1, Avalanche, Polygon, and Arbitrum. The bridge eliminates the need for trusted intermediaries by using Groth16 zero-knowledge proofs to cryptographically verify the validity of cross-chain transfers.
This project represents the cutting edge of cross-chain infrastructure, combining the speed of Solana with the liquidity of EVM chains.
The Challenge
Building a trustless cross-chain bridge presents significant technical challenges:
- No Central Authority: Transfers must be verified without relying on trusted parties
- Multi-Chain Complexity: Support different consensus mechanisms and programming models
- Efficient State Storage: Track transfers without excessive on-chain costs
- User Experience: Abstract complexity behind simple deposit/withdraw flows
System Architecture
Meridian Link consists of five primary subsystems working together seamlessly:
| Subsystem | Technology | Purpose |
|---|---|---|
| Web Frontend | Next.js, React | User interface for initiating transfers |
| Solana Bridge | Anchor, Rust | Handles deposits and withdrawals on Solana |
| EVM Bridge | Solidity, Hardhat | Handles deposits and withdrawals on EVM chains |
| Relayer Service | TypeScript, Express | Off-chain coordinator that generates and submits proofs |
| Light Protocol | Compressed Accounts | Provides state compression for efficient on-chain storage |
Solana Bridge Implementation
The Solana bridge is implemented as an Anchor program named CrossChainTokenBridge. It manages:
Core Program Data Structures:
- BridgeState PDA: Global bridge state tracking deposit counts
- TokenBridge PDAs: Per-route token bridge configurations indexed by
linkHash - WithdrawalProof PDAs: Storage for ZK proof components before withdrawal execution
- Compressed Accounts: Deposit and withdrawal records stored via Light Protocol
Key Instructions:
initBridge- Initialize the global bridge statecreateTokenBridge- Set up a new token bridging routedeposit- Lock tokens and emit deposit event for relayerstoreWithdrawalProof- Store ZK proof for pending withdrawalcompleteWithdrawal- Execute withdrawal after proof verification
Light Protocol integration reduces storage costs by up to 99%, making Meridian Link economically viable for high-volume bridging.
EVM Bridge Implementation
The EVM side uses Solidity smart contracts deployed via Hardhat:
BridgeContract.sol
- Token locking and unlocking
- Deposit event emission
- ZK proof verification for withdrawals
Groth16Verifier.sol
- On-chain verification of zero-knowledge proofs
- Generated from trusted setup ceremony
Relayer Service
The TypeScript relayer service acts as the off-chain coordinator:
- Event Listening: Monitors deposit events on both chains
- Proof Generation: Generates Groth16 proofs for valid deposits
- Proof Submission: Submits proofs to destination chain
- Status Tracking: Maintains transfer status for frontend queries
Zero-Knowledge Proof System
The bridge uses Groth16 proofs to verify:
- Deposit Existence: Proof that a deposit was made on the source chain
- Amount Correctness: The withdrawal amount matches the deposit
- Single Withdrawal: Prevent double-spending via nullifier tracking
Proof Workflow:
- User deposits tokens on source chain
- Relayer observes deposit event
- Relayer generates ZK proof of deposit validity
- Proof submitted to destination chain
- On-chain verifier validates proof
- Tokens released to user
Cross-Chain Transfer Flow
Solana → EVM Transfer
User → Solana Bridge (deposit) → Relayer (proof gen) → EVM Bridge (verify + withdraw)
EVM → Solana Transfer
User → EVM Bridge (deposit) → Relayer (proof gen) → Solana Bridge (verify + withdraw)
Frontend Application
The Next.js frontend provides a seamless user experience:
- Chain Selection: Intuitive source/destination chain picker
- Token Selection: Browse available bridging routes
- Amount Input: Real-time fee estimation
- Transaction Tracking: Monitor transfer status across chains
- Wallet Integration: Support for both Solana (Phantom, Solflare) and EVM (MetaMask, WalletConnect) wallets
Supported Networks
| Network | Type | Status |
|---|---|---|
| Solana Mainnet | Source/Destination | Production |
| Ethereum Mainnet | Source/Destination | Production |
| Avalanche C-Chain | Source/Destination | Production |
| Polygon | Source/Destination | Production |
| Arbitrum One | Source/Destination | Production |
Results & Impact
Meridian Link demonstrates the future of trustless cross-chain infrastructure:
- Zero Trust Required: ZK proofs eliminate reliance on multisigs or oracles
- Cost Efficient: Light Protocol reduces Solana storage costs significantly
- Fast Finality: Optimistic transfer completion with proof generation
- Multi-Chain Ready: Architecture supports adding new chains easily
The whitepaper detailing our cryptographic approach is available for technical review, showcasing our commitment to transparency and security in cross-chain infrastructure.
