If you discover a security vulnerability in CRIPT, please report it by emailing: security@cript-project.dev (or your actual security contact)

DO NOT open a public GitHub issue for security vulnerabilities.

Please provide:

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

We will acknowledge your report within 48 hours and work to resolve it promptly.

• ECDSA Signatures: Uses standardized SECP256R1 (P-256) elliptic curve
• SHA256 Hashing: Cryptographically secure hash function (FIPS-approved)
• HKDF Derivation: Following RFC 5869 specifications
• Forward Secrecy: Each message uses ephemeral keys
• Post-Compromise Security: Old keys destroyed after ratcheting

1. Symmetric Encryption: Currently uses placeholder encryption

   • ACTION: Implement AES-256-GCM for production deployment
   • Reference: NIST SP 800-38D

2. Key Exchange: Initial sender keys must be exchanged via secure out-of-band channel

   • ACTION: Use X3DH (Extended Triple Diffie-Hellman) for key agreement
   • Reference: Signal Protocol documentation

3. Metadata: Server can observe connection patterns

   • MITIGATION: Deploy over Tailscale or similar VPN for network-level privacy
   • MITIGATION: Use onion routing for complete anonymity if required

4. Replay Attack: Protocol requires application-level sequence number checks

   • ACTION: Implement Lamport timestamps or incrementing counters
   • VALIDATION: Check sequence_number field in each message

5. Group Management: No secure group membership protocol

   • ROADMAP: Implement MLS (Messaging Layer Security) subset

• Can read/modify network traffic (unless using Tailscale)
• Can send arbitrary messages
• Can compromise current ephemeral keys

• Forward Secrecy: ✓ Yes (ephemeral keys destroyed)
• Post-Compromise Security: ✓ Yes (automatic ratcheting)
• Message Authentication: ✓ Yes (ECDSA signatures)
• Message Confidentiality: ⚠️ Partial (needs symmetric encryption)
• Perfect Forward Secrecy: ⚠️ Partial (with PCS)

1. Key Management

   # ✓ DO: Secure key storage
   from cryptography.hazmat.primitives.asymmetric import ec
   private_key = ec.generate_private_key(ec.SECP256R1())
   
   # ✗ DON'T: Hardcode keys
   PRIVATE_KEY = b"super-secret-key"

2. Message Verification

   # ✓ DO: Always verify signatures
   from cryptography.exceptions import InvalidSignature
   try:
       receiver.verify_message(message)
   except InvalidSignature:
       # REJECT message - possible tampering
       logger.error("TAMPERING DETECTED")
   
   # ✗ DON'T: Skip verification
   process_message(message)  # INSECURE!

3. Sequence Checking

   # ✓ DO: Check sequence numbers
   if message.sequence_number <= last_received:
       # REJECT - potential replay
       raise ReplayAttackError()
   
   # ✗ DON'T: Accept all messages
   process_message(message)  # Vulnerable to replay

4. Deployment

   # ✓ DO: Use Tailscale for secure transport
   sudo tailscale up
   python -m cript.network.server
   
   # ✗ DON'T: Expose server on public internet
   # Server needs TLS/HTTPS in addition to CRIPT

• Code review completed
• Cryptographic parameters verified
• Edge cases tested
• Error handling reviewed
• Logging doesn't expose secrets
• Dependencies updated
• Vulnerability scanning passed

• NIST SP 800-186: Recommendations for Discrete Logarithm-based Cryptography
• RFC 5869: HMAC-based Extract-and-Expand Key Derivation Function (HKDF)
• FIPS 186-4: Digital Signature Standard (DSS)
• Signal Protocol: https://signal.org/docs/
• Balbás et al. (2022): Analysis and Improvements of the Sender Keys Protocol

If a security incident occurs:

1. Immediate Actions

   • Revoke compromised keys
   • Alert all users
   • Preserve evidence
   • Post-incident review

2. Communication

   • Transparency with users
   • Timeline of events
   • Mitigation steps
   • Prevention measures

3. Recovery

   • Deploy patched version
   • Key rotation process
   • Verification procedures

Last Updated: May 2026 Version: 1.0.0