Signal has announced that it has added quantum-resistant encryption to its end-to-end encryption (E2EE) messaging protocol. This means that Signal’s users can now be confident that their communications are protected even from the most advanced quantum computers.
Signal explains that its “X3DH” (Extended Triple Diffie-Hellman) key agreement protocol has been upgraded to “PQXDH” (Post-Quantum Extended Diffie-Hellman), which incorporates quantum-resistant secret key generation mechanisms for Signal’s end-to-end encryption (E2EE) specification.
Specifically, PQXDH uses both X3DH’s elliptic curve key agreement protocol and a post-quantum key encapsulation mechanism called CRYSTALS-Kyber.
CRYSTALS-Kyber is a NIST-approved quantum-resistant cryptographic algorithm suitable for general encryption and speedy operations that require a quick exchange of small encryption keys.
“We believe that the key encapsulation mechanism we have selected, CRYSTALS-Kyber, is built on solid foundations, but to be safe, we do not want to simply replace our existing elliptic curve cryptography foundations with a post-quantum public key cryptosystem,” explains Signal.
“Instead, we are augmenting our existing cryptosystems such that an attacker must break both systems in order to compute the keys protecting people’s communications.”
