Automated Side-Channel Analysis of Cryptographic Protocol Implementations

Abstract: We extract the first formal model of WhatsApp from its implementation by combining binary-level analysis (via CryptoBap) with reverse engineering (via Ghidra) to handle this large closed-source application. Using this model, we prove forward secrecy, identify a known clone-attack against post-compromise security and discover functional gaps between WhatsApp's implementation and its specification. We further introduce a methodology to analyze cryptographic protocol implementations for their resilience to side-channel attacks. This is achieved by extending the CryptoBap framework to integrate hardware leakage contracts into the protocol model, which we then pass to the state-of-the-art protocol prover, DeepSec. This enables a detailed security analysis against both functional bugs and microarchitectural side-channel attacks. Using this methodology, we identify a privacy attack in WhatsApp that allows a side-channel attacker to learn the victim's contacts and confirm a known unlinkability attack on the BAC protocol used in electronic passports. Key contributions include (1) the first formal model of WhatsApp, extracted from its binary, (2) a framework to integrate side-channel leakage contracts into protocol models for the first time, and (3) revealing critical vulnerabilities invisible to specification-based methods.