'The Signal Foundation, maker of the Signal Protocol that encrypts messages sent by more than a billion people, has rolled out an update designed to prepare for a very real prospect that’s never far from the thoughts of just about every security engineer on the planet: the catastrophic fall of cryptographic protocols that secure some of the most sensitive secrets today.

The Signal Protocol is a key ingredient in the Signal, Google RCS, and WhatsApp messengers, which collectively have more than 1 billion users. It’s the engine that provides end-to-end encryption, meaning messages encrypted with the apps can be decrypted only by the recipients and no one else, including the platforms enabling the service. Until now, the Signal Protocol encrypted messages and voice calls with X3DH, a specification based on a form of cryptography known as Elliptic Curve Diffie-Hellman.

[...]

There is little disagreement, however, that there will come a day when many of the most widely used forms of encryption will die at the hands of quantum computing. To head off that doomsday eventuality, engineers and mathematicians have been developing a new class of PQC, short for post-quantum cryptography.

The PQC added to the Signal Protocol on Monday is called PQXDH. It uses the same X3DH specification the Signal Protocol has always employed. On top, it adds an additional layer of encryption using Crystals-Kyber, one of four PQC algorithms the National Institute of Standards and Technology selected last year as a potential replacement to ECC and other quantum-vulnerable forms of encryption.'

-- source: https://arstechnica.com/security/2023/09/signal-preps-its-encryption-engine-...

Cheers, Peter