Attack that extracts secret information, typically cryptographic keys, by analyzing the physical or temporal emanations of a system in operation rather than attacking the algorithm itself.
Side-channel attacks bypass the mathematical robustness of a cryptographic algorithm by focusing not on its logic but on its physical or temporal side effects during execution. The English term appeared in academic literature in the 1990s, though the underlying principle is older: the TEMPEST project, classified by the NSA since the 1950s, addressed the reconstruction of information from electromagnetic radiation emitted by processing equipment. Paul Kocher formalized timing attacks against RSA in 1996, and differential power analysis against DES with Jaffe and Jun in 1998. Today, side channels include processing time, power consumption, electromagnetic radiation, acoustic emissions from a processor, and even memory cache variations, as in the Specter and Meltdown attacks of 2018 that affected virtually all modern processors. These attacks are invisible to conventional detection systems: no abnormal network packet, no malicious process, no visible intrusion attempt. They directly concern HSMs, Hardware Security Modules, used in banking and insurance to protect master keys, and their exploitation can compromise an entire public key infrastructure. For a cyber insurer, a successful side-channel attack against an HSM constitutes a claim of exceptional severity, since it retrospectively invalidates all encrypted communications under the compromised key.
In 2017, researchers from Tel Aviv University demonstrate an acoustic side-channel attack against GnuPG: by placing a microphone a few centimeters from a laptop during decryption, it is possible to extract a 4096-bit RSA key in one hour. The demonstration remains academic but led to a redesign of the library to ensure operations run in constant time.
side-channel attack, canal auxiliaire, attaque temporelle, timing attack, attaque par consommation, power analysis