International Association
for Cryptologic Research

Given a fixed-size block, cryptographic block functions gen- erate outputs by a sequence of bitwise operations. Block functions are widely used in the design of hash functions and stream ciphers. Their correct implementations hence are crucial to computer security. We pro- pose a method that leverages logic equivalence checking to verify assem- bly implementations of cryptographic block functions. Logic equivalence checking is a well-established technique from hardware verification. Using our proposed method, we verify two dozen assembly implementations of ChaCha20, SHA-256, and SHA-3 block functions from OpenSSL and XKCP automatically. We also compare the performance of our technique with the conventional SMT-based technique in experiments.