If AES is broken, can anyone read your Signal messages? Your WhatsApp chats? Your iMessages? The answer is more encouraging than you might expect.

How Messaging Apps Use Encryption

Modern messaging apps use layered cryptography. AES is one component, but it's not the only defense.

Signal

Signal uses the Signal Protocol with multiple cryptographic layers:

  • X3DH + Double Ratchet: Provides forward secrecy — each message uses a different key. Even if one key is compromised, past and future messages remain protected.
  • PQXDH: Signal has already deployed post-quantum key exchange using ML-KEM, meaning new sessions don't depend solely on classical algorithms.
  • AES-256-CBC: Used for message encryption in the inner layer.

The Möbius Bridge affects the AES layer, but Signal's forward secrecy means an attacker would need to break the key exchange AND the symmetric cipher for each individual message. With PQXDH deployed, the key exchange is post-quantum resistant.

Verdict: Signal is likely the safest messaging app post-Möbius Bridge, thanks to PQXDH and forward secrecy.

WhatsApp

WhatsApp uses the Signal Protocol (licensed from Signal), so it inherits the same cryptographic structure:

  • Same Double Ratchet forward secrecy
  • Same AES-256-CBC for message encryption
  • However: WhatsApp has NOT publicly deployed PQXDH

The Meta-specific concerns (metadata collection, backup encryption) remain, but the end-to-end message encryption is structurally similar to Signal's.

Verdict: Strong encryption, but lacking post-quantum key exchange. Metadata sharing with Meta is a separate concern.

iMessage

Apple deployed PQ3, their post-quantum messaging protocol, in early 2024:

  • Uses ML-KEM for post-quantum key exchange
  • Ratcheting mechanism provides forward secrecy
  • AES-256-GCM for message encryption

PQ3 addresses the key exchange side. The AES layer remains, but Apple will likely migrate to an AES alternative.

Verdict: Strong post-quantum foundation. AES dependency will need addressing, but forward secrecy limits the impact.

Telegram

Telegram's "Secret Chats" use MTProto 2.0 with AES-256-IGE. Regular chats are NOT end-to-end encrypted — they're server-encrypted, meaning Telegram can read them.

Verdict: Avoid for sensitive communications. Regular chats have no end-to-end encryption. Secret Chats use AES without post-quantum key exchange.

The Forward Secrecy Factor

Forward secrecy is the most important property here. With forward secrecy, each message uses a different encryption key derived from an evolving chain. Breaking one message's key doesn't expose other messages.

This means an attacker using the Möbius Bridge against Signal or iMessage would need to:

  1. Capture the encrypted message
  2. Break the key exchange for that specific session (post-quantum resistant in Signal/iMessage)
  3. Break the AES encryption for that specific message
  4. Repeat for every single message

This is vastly harder than breaking a single key and reading everything.

Recommendation

For maximum security: Signal. It has the strongest combination of post-quantum key exchange, forward secrecy, open-source code, and no metadata collection.

Check your overall security posture with our free assessment.