3a76453828
CRYPTO-001: Certificate serial collision detection - Add _generate_unique_serial() helper for database-backed PKI - Add _generate_unique_serial() method for in-memory PKI class - Check database for existing serial before certificate issuance - Retry with new random serial if collision detected (max 5 attempts) TIMING-001: Constant-time database lookups for sensitive queries - Add dummy PBKDF2 verification when paste not found - Prevents timing-based enumeration (attackers can't distinguish 'not found' from 'wrong password' by measuring response time)