Yes. Signal deployed the PQXDH protocol in September 2023, combining X25519 with ML-KEM-768 for quantum-resistant key exchange.
Key Takeaway: Signal is considered quantum safe. Signal uses ML-KEM-768 (aligned with FIPS 203) in hybrid mode.
Signal is quantum safe as of version 6.35+ (September 2023). Signal was the first major messaging platform to deploy post-quantum cryptography at scale, protecting over 40 million users. The PQXDH (Post-Quantum Extended Diffie-Hellman) protocol combines classical X25519 with ML-KEM-768, providing hybrid quantum resistance for all new chat sessions. Messages are protected against harvest now, decrypt later attacks. Signal's implementation was developed in collaboration with researchers from ETH Zurich and has been independently audited.
| Full Name | Signal Private Messenger |
| Category | communication |
| Quantum Vulnerability | Pre-PQXDH messages used X25519 only (vulnerable to Shor's algorithm). All new sessions after September 2023 use hybrid PQC. |
| NIST Status | Signal uses ML-KEM-768 (aligned with FIPS 203) in hybrid mode. |
| Deprecation Timeline | Already quantum safe |
| Replaced By | N/A — Signal has already migrated to PQC (PQXDH with ML-KEM-768) |
Update Signal to version 6.35 or later. New conversations automatically use PQXDH.
Signal is quantum safe, but your cryptographic posture is only as strong as its weakest link. QScout maps your entire cryptographic inventory in 7 days.