Agent-Skills.md

Agent Skills: Implementing Zero-Knowledge Proof for Authentication

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 identificati

UncategorizedID: plurigrid/asi/implementing-zero-knowledge-proof-for-authentication

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plurigrid/asi
plurigridLicense: MIT
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Skill Metadata

Name
implementing-zero-knowledge-proof-for-authentication
Description
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 identificati

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.

When to Use

  • When deploying or configuring implementing zero knowledge proof for authentication capabilities in your environment
  • When establishing security controls aligned to compliance requirements
  • When building or improving security architecture for this domain
  • When conducting security assessments that require this implementation

Prerequisites

  • Familiarity with cryptography concepts and tools
  • Access to a test or lab environment for safe execution
  • Python 3.8+ with required dependencies installed
  • Appropriate authorization for any testing activities

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

  1. Setup: Public generator g, prime p, q (order of g)
  2. Registration: Prover computes y = g^x mod p (public key from secret x)
  3. Commitment: Prover sends t = g^r mod p (random r)
  4. Challenge: Verifier sends random c
  5. Response: Prover sends s = r + c*x mod q
  6. 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