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Security Considerations

Draft

This section is under construction and requires additional research.

Threat Model​

SimpleX is designed to resist:

  • Server compromise: Servers cannot read message content (triple encryption)
  • Traffic analysis: Fixed 16KB block size prevents size-based correlation
  • User correlation: No user identifiers; each queue uses unique keys
  • Network surveillance: TLS 1.3 protects transport; private routing adds 2-hop onion

Private Message Routing​

SimpleX supports 2-hop onion routing where messages traverse two SMP servers, preventing any single server from knowing both sender and recipient.

Forward Secrecy​

The Double Ratchet provides forward secrecy: compromise of current keys does not reveal past messages. Each message uses a unique message key derived from the chain KDF.

Post-Quantum Extensions​

E2E Encryption version 3 adds post-quantum KEM (Key Encapsulation Mechanism) to the ratchet, providing resistance against future quantum computers.