An AI Approach to Verified Production Cryptographic Libraries

2026-08-01

AI Summary

This work addresses the challenges of scale and complexity in formally verifying production-grade cryptographic libraries, where existing approaches fall short of end-to-end automation. We present CryptoProver, a system that achieves, for the first time, fully automated verification of real-world cryptographic implementations such as curve25519-dalek and RustCrypto’s chacha20. CryptoProver integrates large language models with the Verus verifier to automatically synthesize internal specifications and verifiable proofs from high-level API contracts, without requiring source code modifications. By leveraging a pre-defined trusted library, mechanical gating, and isolation mechanisms, the system ensures specification strength and cross-module consistency. In experiments, CryptoProver completed verification within 11.4 hours at an API cost of \$466.99, successfully covering core cryptographic components relied upon by widely deployed systems including Signal (with 218 million downloads) and Shadowsocks.

Abstract

Cryptographic code is critical infrastructure that must be correct, yet formally verifying production libraries remains difficult. Existing language-model proof systems solve isolated obligations with specifications and premises already given, leaving production-library verification unresolved. We present CryptoProver, an AI-based system that synthesizes internal specifications and Verus-checked proofs from high-level API contracts. Without changing executable code, CryptoProver constructs a new independent proof of curve25519-dalek and verifies RustCrypto's previously unverified chacha20 implementation against an RFC 8439 specification. These cryptographic lineages underpin deployed systems including Signal and Shadowsocks; Signal has an estimated 218M global downloads. The independent, human-led curve25519-dalek verification was developed publicly over eight months by five main contributors. Given the API contracts and a fixed trusted library of field specifications, arithmetic facts, axioms, and vstd, CryptoProver synthesizes the internal specifications and proofs in 11.4 hours with USD 466.99 in recorded API cost. CryptoProver follows a trust-first design principle: mechanical gates reject specification weakening, invented axioms, and cross-module breakage, while isolation blocks reference proof retrieval, including from git history.

Problem

• formal verification
• cryptographic libraries
• production code
• specification synthesis
• AI-assisted verification

Innovation

• CryptoProver
• formal verification
• AI-assisted proof synthesis
• trust-first design
• production cryptographic libraries