Constant Time Model Analysis
Abstract
Constant time programming patterns is the primary defense against timing attacks on cryptographic implementations, yet what constant time means varies across academia and industry. This work systematizes constant time models and their evolution, identifies a recurring gap between what models protect and what specifications assume, and distills an offensive methodology for discovering timing vulnerabilities that originate outside the cryptographic primitive boundary. Applying this methodology, we locate a specification-level vulnerability related to private key loading, and confirm the leak in both OpenSSL and BoringSSL. Counterintuitively, BoringSSLs per-observation signal is several orders of magnitude stronger than OpenSSLs, despite an explicitly stricter threat model.