The Signal Protocol is a set of cryptographic specifications that provides end-to-end encryption for private communications exchanged daily by billions of people around the world. After its publication in 2013, the Signal Protocol was adopted not only by Signal but well beyond. Technical informat...

The article is about:

  • The Signal Protocol, a set of cryptographic specifications that provides end-to-end encryption for private communications. PQXDH, an upgrade to the Signal Protocol that adds a layer of protection against the threat of a future quantum computer breaking current encryption standards.
  • Quantum computing, a new type of computational system that can solve some complex problems faster than classical computers, such as the hidden subgroup problem that underlies many public key cryptosystems4.
  • Post-quantum cryptography, a new category of algorithms that resist quantum attacks, and how Signal has chosen CRYSTALS-Kyber as its post-quantum key encapsulation mechanism.
  • The implementation and deployment of PQXDH in Signal’s client applications and the open research areas for further quantum resistance.