Reactive Bridge: Making Escrow Cross-Chain

Escrows are powerful tools for trustless transactions, but most early designs were stuck on a single blockchain. That limits usability: what if the buyer is on Ethereum, the freelancer prefers Avalanche, and the adjudicator is on Base? Enter Reactive Bridge, SmarTrust’s cross-chain event relay system.

Why do escrows need to be cross-chain?

• Diverse ecosystems: Users hold funds on different chains (ETH, BNB, AVAX, stablecoins on Base).
• Liquidity fragmentation: Keeping everything on one chain reduces flexibility and increases costs.
• Real-world workflows: Buyers, sellers, and adjudicators don’t always operate in the same ecosystem.
• Arbitration neutrality: Arbitrators can be chosen and paid regardless of chain alignment.

What is the Reactive Bridge?

Reactive Bridge is a smart contract and relay system that listens to events on one chain and reacts on another. For example:

• An EscrowDeployed event on Ethereum can register the escrow on Avalanche.
• A DisputeReceived event on Base can be forwarded to the adjudicator contract on Sepolia.
• A RulingIssued event on the adjudicator side can trigger payouts on the original escrow chain.

How it works (simplified flow)

1. Escrow Factory emits events
   Deploying or updating an escrow emits structured events (e.g., EscrowDeployed, AdjudicationRequested).

2. Reactive Bridge subscribes
   The bridge contract records subscriptions linking escrow addresses to a cross-chain destination.

3. Event relayed
   A log record (chain_id, contract, topics, data) is captured and transmitted securely.

4. Target contract reacts
   The event payload is passed into the adjudicator or mirror escrow on the other chain.

5. Resolution flows back
   Rulings, payouts, or updates are relayed back so funds move according to the decision.

Benefits of this design

• Chain-agnostic escrows: Parties aren’t forced onto a single network.
• Scalability: Escrow contracts can be lightweight clones, while the heavy arbitration logic sits elsewhere.
• Resilience: Even if one chain is congested, adjudication can continue elsewhere.
• Composability: Other dApps can subscribe to the same events for analytics, insurance, or compliance.

Key components

• EscrowFactory: Deploys new escrows and emits EscrowDeployed events.
• EscrowTemplate: Standardized escrow logic (funding, payouts, disputes).
• Adjudicator: Handles disputes, assigns arbitrators, and issues rulings.
• ReactiveBridge: Relays cross-chain events (ESub, DRelay, RRelay, Callback).

Challenges & considerations

• Gas fees: Each relay must be economical, so batching and compression are valuable.
• Finality risk: Different chains have different block finality times—design must handle reorgs.
• Security: Relays must be tamper-proof and verifiable.
• UX complexity: Abstracting away chain IDs and addresses is essential for non-technical users.

The bigger picture

Cross-chain escrows enable truly global trustless commerce. A buyer in Canada using USDC on Base, a freelancer in Nigeria using BNB on Binance, and an adjudicator operating on Sepolia can all interact seamlessly. That’s the promise of Reactive Bridge: removing silos so trustless agreements work everywhere.

Bottom line: Reactive Bridge takes escrows from being “chain-locked” contracts to becoming cross-chain services, where funds, disputes, and rulings can flow securely across ecosystems.