Credence

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 fake
• Certificates are static PDFs no way to know if they’re real, expired, or revoked
• Grades and test details are public when shared
• Renewing skills is manual and forgotten
• Web3 credentials cost gas and expose everything

Credence fixes all of this.

How It Works

1. Earn a Skill
   You complete a course or test (e.g., on Udemy, Coursera, or your uni degree).
   The issuer instantly grants you a private NFT badge.

2. It’s Private by Default Your grade, test answers, and personal data are encrypted using Lighthouse
   Only you can decrypt and share them, never public unless you choose.

3. 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.

4. 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.

5. 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   • Has it been revoked?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 |

How It's Made – Credence

We 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 5
• ERC-721 + ERC-4907 for rental-style expiry
• Hardhat v3 + Ignition for deterministic deploys

Key contracts:

• CertificationRegistry.sol – backend-only issuer registry
• SkillNFT.sol – mints with encrypted Lighthouse CID
• RentalManager.sol – extends expiry on existing token
• IssuanceAPI.sol – backend mint entrypoint
• CredentialVerifier.sol – isValid(tokenId) view

All 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 Mumbai

Flow:

1. User connects → Biconomy creates smart account
2. Issuer calls /api/issue
3. Backend builds UserOp → Biconomy submits via Paymaster
4. No gas prompt → badge appears instantly

---

3. Privacy (Lighthouse)

Sensitive data (grade, answers) encrypted with Lighthouse.

• Backend uploads encrypted blob → CID
• NFT stores only CID
• Only user can decrypt

---

4. 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 Router
• Prisma + Postgres for orgs, API keys, logs
• Admin: approve issuers, generate keys, view stats

---

6. Deployment

• Contracts: Mumbai → Polygon
• Backend: Vercel
• Envio: Hosted indexer
• Lighthouse: API key
• Biconomy: Paymaster on Mumbai

---

Notable Implementation Details

1. Off-chain-first flow
   Encrypt → Lighthouse → emit event → then submit UserOp. Instant UI, no blockchain wait.

2. Pre-mint event emission
   CredentialIssued fired from backend before Biconomy — Envio shows badge immediately.

3. Soulbound rentals
   SkillNFT blocks transfer while rental is active.

---

Credence delivers private, renewable, gasless skill credentials — instant, secure, and verifiable.