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Each rewritten description now states both what the skill does (concrete capability, named tools/artifacts) and an explicit when-to-use trigger, improving agent discovery/activation. Grounded in each skill's own body; changes confined to the `description` field only (bodies and all other frontmatter untouched). Produced by a gated audit->rewrite->recheck loop (548 -> 0 flagged) with a sampled anti-invention check (0 ungrounded). Schema: 817/817 pass. Framework-ID gate: 0 defects.
87 lines
3.4 KiB
Markdown
87 lines
3.4 KiB
Markdown
---
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name: implementing-zero-knowledge-proof-for-authentication
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description: Implements the Schnorr identification protocol and a simplified Zero-Knowledge Password Proof (ZKPP) over the discrete logarithm problem, letting a prover authenticate by demonstrating knowledge of a secret without ever revealing it to the server. Use when designing or building password-less or password-secret-free authentication, or when a server must verify a user's credential without learning or storing the underlying secret.
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domain: cybersecurity
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subdomain: cryptography
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tags:
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- cryptography
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- zero-knowledge-proof
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- authentication
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- privacy
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- zkp
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version: '1.0'
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author: mahipal
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license: Apache-2.0
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nist_csf:
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- PR.DS-01
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- PR.DS-02
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- PR.DS-10
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mitre_attack:
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- T1600
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- T1573
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- T1553
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---
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# Implementing Zero-Knowledge Proof for Authentication
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## Overview
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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.
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## When to Use
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- When deploying or configuring implementing zero knowledge proof for authentication capabilities in your environment
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- When establishing security controls aligned to compliance requirements
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- When building or improving security architecture for this domain
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- When conducting security assessments that require this implementation
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## Prerequisites
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- Familiarity with cryptography concepts and tools
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- Access to a test or lab environment for safe execution
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- Python 3.8+ with required dependencies installed
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- Appropriate authorization for any testing activities
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## Objectives
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- Implement Schnorr's identification protocol for ZKP authentication
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- Build a non-interactive ZKP using Fiat-Shamir heuristic
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- Implement zero-knowledge password proof (ZKPP)
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- Demonstrate completeness, soundness, and zero-knowledge properties
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- Compare ZKP authentication with traditional password verification
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## Key Concepts
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### ZKP Properties
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| Property | Description |
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|----------|------------|
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| Completeness | Honest prover always convinces honest verifier |
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| Soundness | Dishonest prover cannot convince verifier (except negligible probability) |
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| Zero-Knowledge | Verifier learns nothing beyond the statement's truth |
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### Schnorr Protocol
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1. **Setup**: Public generator g, prime p, q (order of g)
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2. **Registration**: Prover computes y = g^x mod p (public key from secret x)
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3. **Commitment**: Prover sends t = g^r mod p (random r)
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4. **Challenge**: Verifier sends random c
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5. **Response**: Prover sends s = r + c*x mod q
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6. **Verify**: Check g^s == t * y^c mod p
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## Security Considerations
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- Use cryptographically secure random number generators
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- Challenge must be unpredictable (from verifier's perspective)
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- For non-interactive proofs, use Fiat-Shamir with collision-resistant hash
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- ZKP alone does not provide forward secrecy; combine with TLS
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## Validation Criteria
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- [ ] Honest prover always verifies successfully (completeness)
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- [ ] Random response without secret does not verify (soundness)
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- [ ] Server never receives the secret value
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- [ ] Non-interactive proof is verifiable offline
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- [ ] Multiple authentications produce different transcripts
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- [ ] Protocol resists replay attacks
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