Signal
Is PQC enabled? — quick check
App version check (any platform)
# Signal: Settings → Help → Version
# WhatsApp: Settings → Help → App info
# iMessage: Settings → General → About → Software VersionExpected when PQC is ON
Signal 6.47+ / WhatsApp 24.10+ / iOS 17.4+
PQXDH (Signal/WhatsApp) or PQ3 (iMessage) active for new chats.What you'll see when PQC is OFF
Signal 6.46 / WhatsApp 24.9 / iOS 17.3
Initial key agreement is classical X3DH only.These apps don't expose a per-chat PQ indicator. The version on both ends is the authoritative answer.
Signal rolled out PQXDH ("post-quantum extended Diffie-Hellman") in August 2023. PQXDH augments the original X3DH initial key agreement with a Kyber-1024 KEM share. Every new conversation since then derives its root key from X25519 and Kyber, so an adversary recording today's handshakes can't decrypt them later with a quantum computer.
What you need to do
Nothing. PQXDH is on by default in:
- Signal for iOS 6.47+
- Signal for Android 6.47+
- Signal Desktop 7.x+
If both peers are on the supported version, the conversation is PQ-safe.
Verify
- Settings → Help → Debug log includes a "PQXDH used" marker after the next handshake.
- The safety number for any chat created post-2023-08 was negotiated through PQXDH; rotating it (delete the chat and message again) re-runs PQXDH.
What's still classical
- The Double Ratchet itself uses Curve25519 inside the session — Signal has signaled a future "PQ Ratchet" but it isn't shipped yet (as of early 2026).
- Group chats use Sender Keys, also Curve25519.