DeepMind says AlphaProof Code verified Signal's compiled code

On Nov. 10, Google DeepMind said AlphaProof Code used Gemini Carbon agents to produce machine-checked Lean proofs for compiled libsignal, the Signal protocol's reference implementation. The technical paper says the proofs are about 6.5 million lines and cover the PQXDH handshake and Triple Ratchet for forward secrecy, authentication, post-compromise security, and handshake secrecy. They apply to unmodified libsignal linked into a command-line harness and compiled with stock rustc to AArch64, with some cryptographic routines specified by contracts, not to every installed Signal app. DeepMind says two previously fixed bugs, when put back into an isolated copy, produced proofs that those binaries were insecure. The paper's first-proofs wording is the authors' claim.