Credence

Problem Statement

Credence is a universal, private, and renewable proof-of-skill system built on blockchain, designed to solve the core problems of skill verification in a digital world.The Problem It Solves In today’s world:Resumes are easy to fakeCertificates are static PDFs no way to know if they’re real, expired, or revokedGrades and test details are public when sharedRenewing skills is manual and forgottenWeb3 credentials cost gas and expose everythingCredence fixes all of this.How It WorksEarn a SkillYou complete a course or test (e.g., on Udemy, Coursera, or your uni degree).The issuer instantly grants you a private NFT badge.It’s Private by Default Your grade, test answers, and personal data are encrypted using LighthouseOnly you can decrypt and share them, never public unless you choose.It’s Renewable Skills expire (e.g., 90 days).When near expiry (not uni degrees but mostly online courses), you’re prompted to retake a test.Pass → badge is renewed automatically — same NFT, new expiry.It’s Gasless Until You Need It Badges are issued off-chain using Yellow ClearNode - zero cost.You only pay gas once (testnet), when you want to "settle" the badge to the public blockchain.It’s Universally Verifiable Once settled, anyone can verify:Was this issued by a trusted org?Is it still valid?Has it been revoked?→ All on-chain, trustless, instant.Key Features| Feature | Benefit | |-------|--------| | Private Metadata | Grades & details stay hidden | | Renewable Badges | Skills stay current | | Gasless Issuance | Free for users & issuers | | One-Click Settlement | Make it public when needed | | Universal Standard | Works across all platforms | | Issuer Registry | Only verified orgs can issue | | Real-time Dashboard | See all badges instantly (Envio indexes issuance events even when off-chain and unsettled, enabling live updates before on-chain confirmation) |Who Uses It?| User | Use Case | |-----|---------| | Students | Prove skills to employers | | Professionals | Keep certs up-to-date | | Issuers (Udemy, etc.) | Issue trusted, trackable badges | | Employers | Verify candidates in 1 click |

Solution

How It's Made – CredenceWe built Credence with a clean, modular stack focused on privacy, instant feedback, and zero user cost.1. Smart Contracts (Hardhat + Ignition)Solidity 0.8.24 with OpenZeppelin 5ERC-721 + ERC-4907 for rental-style expiryHardhat v3 + Ignition for deterministic deploysKey contracts:CertificationRegistry.sol – backend-only issuer registrySkillNFT.sol – mints with encrypted Lighthouse CIDRentalManager.sol – extends expiry on existing tokenIssuanceAPI.sol – backend mint entrypointCredentialVerifier.sol – isValid(tokenId) viewAll mints go through IssuanceAPI via backend — no frontend minting.2. Gasless Flow (Biconomy ERC-4337)We use Biconomy’s account abstraction:Smart accounts (no seed phrase)Paymaster (sponsored gas)Bundler on Polygon MumbaiFlow:User connects → Biconomy creates smart accountIssuer calls /api/issueBackend builds UserOp → Biconomy submits via PaymasterNo gas prompt → badge appears instantly3. Privacy (Lighthouse)Sensitive data (grade, answers) encrypted with Lighthouse.Backend uploads encrypted blob → CIDNFT stores only CIDOnly user can decrypt4. Real-Time UI (Envio)We emit CredentialIssued from 355 before UserOp is sent.Envio indexes it → GraphQL updates instantly.Badge shows in UI <1 second after issuance — even if tx is pending.5. Backend & Admin (Next.js + Prisma)Next.js 14 App RouterPrisma + Postgres for orgs, API keys, logsAdmin: approve issuers, generate keys, view stats6. DeploymentContracts: Mumbai → PolygonBackend: VercelEnvio: Hosted indexerLighthouse: API keyBiconomy: Paymaster on MumbaiNotable Implementation DetailsOff-chain-first flowEncrypt → Lighthouse → emit event → then submit UserOp. Instant UI, no blockchain wait.Pre-mint event emissionCredentialIssued fired from backend before Biconomy — Envio shows badge immediately.Soulbound rentalsSkillNFT blocks transfer while rental is active.Credence delivers private, renewable, gasless skill credentials — instant, secure, and verifiable.