Implementing Zero-Knowledge Proof for Authentication
Overview
Zero-Knowledge Proofs (ZKPs) allow a prover to demonstrate knowledge of a secret (such as a password or private key) without revealing the secret itself. This skill implements the Schnorr identification protocol and a simplified ZKPP (Zero-Knowledge Password Proof) using the discrete logarithm problem, enabling authentication where the server never learns the user's password.
Objectives
- Implement Schnorr's identification protocol for ZKP authentication
- Build a non-interactive ZKP using Fiat-Shamir heuristic
- Implement zero-knowledge password proof (ZKPP)
- Demonstrate completeness, soundness, and zero-knowledge properties
- Compare ZKP authentication with traditional password verification
Key Concepts
ZKP Properties
| Property | Description |
|---|---|
| Completeness | Honest prover always convinces honest verifier |
| Soundness | Dishonest prover cannot convince verifier (except negligible probability) |
| Zero-Knowledge | Verifier learns nothing beyond the statement's truth |
Schnorr Protocol
- Setup: Public generator g, prime p, q (order of g)
- Registration: Prover computes y = g^x mod p (public key from secret x)
- Commitment: Prover sends t = g^r mod p (random r)
- Challenge: Verifier sends random c
- Response: Prover sends s = r + c*x mod q
- Verify: Check g^s == t * y^c mod p
Security Considerations
- Use cryptographically secure random number generators
- Challenge must be unpredictable (from verifier's perspective)
- For non-interactive proofs, use Fiat-Shamir with collision-resistant hash
- ZKP alone does not provide forward secrecy; combine with TLS
Validation Criteria
- [ ] Honest prover always verifies successfully (completeness)
- [ ] Random response without secret does not verify (soundness)
- [ ] Server never receives the secret value
- [ ] Non-interactive proof is verifiable offline
- [ ] Multiple authentications produce different transcripts
- [ ] Protocol resists replay attacks
Compliance Framework Mapping
This skill supports compliance evidence collection across multiple frameworks:
- SOC 2: CC6.7 (Restriction on Transmission), CC6.1 (Logical Access)
- ISO 27001: A.10.1 (Cryptographic Controls)
- NIST 800-53: SC-12 (Cryptographic Key Management), SC-13 (Cryptographic Protection), SC-8 (Transmission Confidentiality)
- NIST CSF: PR.DS (Data Security)
Claw GRC Tip: When this skill is executed by a registered agent, compliance evidence is automatically captured and mapped to the relevant controls in your active frameworks.
Deploying This Skill with Claw GRC
Agent Execution
Register this skill with your Claw GRC agent for automated execution:
# Install via CLI
npx claw-grc skills add implementing-zero-knowledge-proof-for-authentication
# Or load dynamically via MCP
grc.load_skill("implementing-zero-knowledge-proof-for-authentication")Audit Trail Integration
When executed through Claw GRC, every step of this skill generates tamper-evident audit records:
- SHA-256 chain hashing ensures no step can be modified after execution
- Evidence artifacts (configs, scan results, logs) are automatically attached to relevant controls
- Trust score impact — successful execution increases your agent's trust score
Continuous Compliance
Schedule this skill for recurring execution to maintain continuous compliance posture. Claw GRC monitors for drift and alerts when re-execution is needed.