Zero-Knowledge Proof System

CrowdProof uses Groth16 SNARKs to enable selective disclosure of reputation data. A user can prove their score exceeds a threshold without revealing the actual score.

Why ZK Proofs?

Problem	ZK Solution
DeFi protocol needs to verify creditworthiness	User proves "score ≥ 700" without sharing exact score
DAO requires governance participation history	User proves "governance score ≥ 500" privately
Age-restricted service needs compliance	User proves "age ≥ 21" without sharing birthdate

How It Works

                           ┌─────────────────┐
                           │  CrowdProof API  │
                           │  (Prover)        │
                           └────────┬─────────┘
                                    │
            ┌───────────────────────┼───────────────────────┐
            │                       │                       │
     1. Score Lookup         2. Circuit Eval          3. Proof Gen
     (from DB)               (score ≥ threshold?)    (Groth16 SNARK)
            │                       │                       │
            └───────────────────────┼───────────────────────┘
                                    │
                              ┌─────▼──────┐
                              │   Proof     │
                              │   (bytes)   │
                              └─────┬──────┘
                                    │
                    ┌───────────────┼───────────────┐
                    │                               │
              Off-Chain Verify                On-Chain Verify
              POST /verify                    ReputationOracle
              (API endpoint)                  .verifyProof()

Proof Circuit

The circuit enforces:

1. Score inclusion — The claimed score exists in the Merkle tree committed on-chain
2. Threshold comparison — The score is ≥ the stated threshold
3. Freshness — The score was calculated within a configurable time window

Public Inputs (visible to verifier)

• Merkle root (from on-chain oracle)
• Threshold value
• Score category
• Timestamp bound

Private Inputs (hidden from verifier)

• Actual score
• Merkle proof (inclusion path)
• Wallet address

Supported Proof Types

Score Above Threshold

Proves a wallet's score in a given category meets or exceeds a threshold.

{
  "subject": "0x1234...",
  "proofType": "ScoreAboveThreshold",
  "category": "DEFI_LENDING",
  "threshold": 700
}

Age Verification

Proves a user meets a minimum age requirement using ZK, without revealing their actual age or birthdate.

{
  "walletAddress": "0x1234...",
  "minimumAge": 21
}

Security Properties

Property	Guarantee
Completeness	Valid proofs always verify successfully
Soundness	Cannot create valid proofs for false statements
Zero-Knowledge	Verifier learns nothing beyond the statement's truth
Non-Interactive	Proof generated once, verified any number of times
Succinctness	Proof size is constant (~192 bytes) regardless of circuit size

Trusted Setup

Groth16 requires a one-time trusted setup ceremony:

• Powers of Tau — Phase 1 ceremony with 100+ participants
• Circuit-Specific — Phase 2 ceremony for each proof circuit
• Verification — Setup parameters are publicly auditable

The toxic waste from the ceremony is destroyed. As long as at least one participant was honest, the system is secure.

Performance

Operation	Time
Proof generation	~2 seconds
Off-chain verification	~10 milliseconds
On-chain verification	~250,000 gas