Problem Statement
Cross-border fiat↔crypto trades usually depend on trusted intermediaries or manual reconciliation. We wanted to reduce counterparty risk by enforcing order state transitions on-chain while still validating off-chain fiat payment evidence.
Solution & Approach
We implemented a Solidity `Marketplace` order state machine (`AVAILABLE -> ACCEPTED -> PAID -> COMPLETED`) and connected it to a Next.js frontend. For fiat confirmation, we integrated Flare FDC request/proof flow (`prepareRequest`, `submitRequest`, `submitProof`) and then called `recordFiatPayment` on-chain before token claim.
Tech Stack
Solidity
Next.js
TypeScript
ethers.js
SupabaseTech choices were selected for fast hackathon iteration, clear separation of concerns, and deployable paths beyond demo scope.
System Design
System architecture is shown as a single cleaned diagram for readability.
Key Learnings
The biggest learning was designing around hybrid trust boundaries: on-chain logic can be strict, but off-chain payload quality and attestation timing dominate user experience. If we extended this, we would harden secret management and replace indefinite retries with bounded retries + explicit status states.
