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
I 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.
Resources and links
The repository, verified contract, deployment transaction, lifecycle transactions, and machine-readable deployment manifest are public.
Scope and current status
This is a public testnet reference implementation. It has not been externally audited for production use.