RSA key extraction via low-bandwidth acoustic cryptanalysis

Abstract

Many computers emit a high-pitched noise during operation, due to vibration in some of their electronic components. These acoustic emanations are more than a nuisance: as we show in this paper, they can leak the key used in cryptographic operations. This is surprising, since the acoustic information has very low bandwidth (under 20 kHz using common microphones, and a few hundred kHz using ultrasound microphones), which is many orders of magnitude below the GHz-scale clock rates of the attacked computers. We describe a new acoustic cryptanalysis attack which can extract full 4096-bit RSA keys from the popular GnuPG software, within an hour, using the sound generated by the computer during the decryption of some chosen ciphertexts. We experimentally demonstrate such attacks, using a plain mobile phone placed next to the computer, or a more sensitive microphone placed 10 meters away. © 2014 International Association for Cryptologic Research.