Summary
Celo Credentials is a full-stack reference application for gasless, non-transferable education credentials. Institutions sign EIP-712 vouchers off-chain, a relayer pays the gas, and credentials remain publicly verifiable and revocable on Celo.
Role and scope
Gilles Musy designed and implemented the smart contract, deployment path, relayer backend, indexer boundary, frontend integration, tests, and public evidence manifest.
Problem and constraints
A recipient should receive a verifiable credential without holding funds, while the system still enforces issuer authorization, replay protection, expiry, non-transferability, and revocation.
Architecture
A Foundry-tested Solidity contract validates EIP-712 vouchers. An Express and viem relayer submits transactions, PostgreSQL supports indexing, and a Next.js interface provides connection, issuance, listing, and verification flows.
Decisions and trade-offs
Gas sponsorship stays in a separate relayer, credentials cannot be transferred, nonces are single use, deadlines expire, and revocation is limited to the contract owner or the still-authorized original issuer.
Security context
These controls are security design for a self-authored application. They are not presented as an external audit of the system.
Testing and verification
The public repository reports 11/11 Foundry tests covering minting, soulbound behavior, replay and expiry rejection, unauthorized signers, issuer-bound revocation paths, and fuzzing. CI also validates backend dependencies and the production frontend build.
Public results
The source-verified Celo Sepolia deployment demonstrates issuer authorization, credential issuance, active read-back, and final revocation through public transactions and chain state.
Public evidence
The repository, verified contract, deployment transaction, lifecycle transactions, and machine-readable deployment manifest are public.
Remaining limitations
This is a public testnet reference implementation. It has not been externally audited for production use.