Signal’s New PQ Ratchet
Signal Protocol and Post-Quantum Ratchets Graeme Connell and Rolfe Schmidt on 02 Oct 2025We are excited to announce a significant advancement in the security of the Signal Protocol: the introduction of the Sparse Post Quantum Ratchet (SPQR). This new ratchet enhances the Signal Protocol’s resilience against future quantum computing threats while maintaining our existing security guarantees of forward secrecy and post-compromise security.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 open source Signal Protocol was adopted not only by the Signal application but also by other major messaging products. Technical…
