Implement zero-knowledge identity verification for age-restricted payments

[Smartdevs17]

Description

Certain payment types require age verification without revealing birth date. Implement ZK-proof based identity verification using Circom circuits.

Acceptance Criteria

• Circom circuit for age verification (over-18, over-21)
• ZK proof generation in backend service
• On-chain proof verification in contract
• Circuit testing with edge cases (boundary ages)
• Performance optimization for proof generation
• Integration with identity provider

Technical Scope

• contracts/src/zk-circuits/age-verification.circom
• backend/src/services/zk-identity-service.ts
• backend/src/routes/zk-identity.ts
• Edge: proof malleability, circuit trusted setup, revocation of identity attestations