Legion ZK Auth implements zero-knowledge authentication with the following guarantees:

• ZK Proof System: Halo2 PLONK (no trusted setup)
• Soundness Error: 2^-128 (forgery probability)
• Hash Functions: Blake3 (credentials), Poseidon (circuit)
• Curves: Pasta (Pallas/Vesta)
• Key Derivation: BIP-39 (24-word mnemonic)

• User Anonymity: 1 of 2^20 (1,048,576) users
• Device Anonymity: 1 of 2^10 (1,024) devices per user
• Hardware Binding: WebAuthn TPM/Secure Enclave
• Zero-Knowledge: Server never learns identity

• ✅ Replay Attacks: Prevented by nullifiers + timestamps
• ✅ Session Theft: Prevented by linkability tag binding
• ✅ Credential Stuffing: BIP-39 entropy + rate limiting
• ✅ Timing Attacks: Constant-time operations in circuit
• ✅ Sybil Attacks: Device binding + nullifier tracking

DO NOT open public GitHub issues for security vulnerabilities.

Instead, email: security@yourdomain.com

Include:

• Description of vulnerability
• Steps to reproduce
• Potential impact
• Suggested fix (if any)

We will respond within 48 hours.

1. Always use HTTPS (required for WebAuthn)
2. Set Redis password (requirepass in redis.conf)
3. Run as non-root user (systemd User=legion)
4. Restrict file permissions (chmod 700 /var/lib/legion/data)
5. Enable firewall (only 80/443 open)
6. Configure rate limiting (nginx limit_req)
7. Monitor logs (journalctl -u legion -f)
8. Regular backups (RocksDB + Redis)

1. Use k=16 minimum in production (k=12/14 for testing only)
2. Verify HTTPS before authentication
3. Clear localStorage on logout
4. Validate server responses

1. Validate all inputs (hex strings, field elements)
2. Check timestamp freshness (±10 minutes for k=16/18)
3. Verify nullifier uniqueness (prevent replay)
4. Enforce session TTL (Redis expiration)
5. Log authentication attempts (audit trail)

• Circuit size: 2^16 = 65,536 rows
• Proof time: ~4 minutes
• Proof size: ~3.5 KB
• Security level: 128-bit
• Soundness error: 2^-128

• Circuit size: 2^18 = 262,144 rows
• Proof time: ~15 minutes
• Proof size: ~4 KB
• Security level: 128-bit
• Soundness error: 2^-128

• Code review completed
• Dependencies audited (cargo audit)
• Secrets not in code
• HTTPS certificate valid
• Redis secured
• Rate limiting configured
• Monitoring setup

• Penetration testing
• Load testing
• Log monitoring active
• Backup strategy tested
• Incident response plan
• Security updates scheduled

We follow a 90-day disclosure timeline:

1. Day 0: Vulnerability reported
2. Day 1-7: Acknowledge and validate
3. Day 7-30: Develop and test fix
4. Day 30-60: Deploy fix to production
5. Day 60-90: Public disclosure (coordinated)

We appreciate security researchers who help improve Legion:

• Responsible disclosure
• Coordinated timeline
• Public acknowledgment (with permission)

• Halo2 Documentation
• WebAuthn Specification
• BIP-39 Specification
• Blake3 Paper

• Security: nantha.ponmudi@gmail.com
• GitHub: https://github.com/deadends/legion