Google Just Made History in AI and Software Security
Source: YouTube · Cloud Codes · published Nov 14, 2026 · 17:57
BLUF: DeepMind’s AlphaProof successfully generated machine-checked proofs for the security of Signal’s one-to-one chat protocol, demonstrating that AI can verify complex cryptographic code, but the system’s ultimate reliability depends on humans correctly defining the specifications and trusting a small kernel of unverified assumptions.
Key Takeaways:
• The proof covers the compiled binary of libsignal (version 0.105.4) for 64-bit ARM Linux, establishing a link between protocol-level security and actual machine code bytes 2:01.
• Agents generated approximately 6.5 million lines of Lean proof, yet humans only needed to review about 18,000 lines of specifications, reducing the manual verification burden to under 1% of the total codebase 1:37.
• The system includes robust safeguards against AI cheating, such as a "gatekeeper" that ensures proofs match approved specifications and the Lean kernel that validates every logical step 8:46.
• Proof coverage is limited; it excludes key generation, side-channel attacks, group chats, and the specific binaries found in mobile app stores, which are built differently 12:32.
• The team validated the system’s capability by reversing two real Signal bugs and generating proofs that the security theorems failed, confirming the checker can detect insecurity 10:43.
This work marks a significant milestone in formal verification by bridging the gap between abstract cryptographic models and concrete compiled code. However, it underscores that while AI can automate the verification of known properties, the critical task of defining "correctness" remains a human responsibility.
Sources:
- 2:01 Details the scope of the proof, covering the compiled binary of libsignal for 64-bit ARM Linux.
- 1:37 Explains the human verification load, noting that only about 18,000 lines of specifications required human review.
- 8:46 Describes the anti-cheating mechanisms, including the gatekeeper and Lean kernel checks.
- 12:32 Lists the out-of-scope items, such as key generation, side channels, and mobile app binaries.
- 10:43 Discusses the validation of the system by reversing real bugs to prove the checker can identify insecurity.
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First 800 characters of the transcript
I went into DeepMind's new signal paper asking who checks a proof that none of the authors wrote. When you hear Google's AI prove the code behind Signal's encryption, that's the proof you're being asked to trust. In the same paper, the authors report that one agent cheated. Its trick was redefining a condition in a goal's assumptions as false, which makes that goal trivially true and useless. Google DeepMind announced the work on November 10th as AlphaProof code. Its agents wrote about 6 and 1/2 million lines of proof in Lean, a language where a program called the kernel checks every step. Headlines ran with a figure from DeepMind's own blog. Only 1% got a human look. So besides the paper, I read the code repository and Signal's own fix commits to see what was proved and what still rests o…