RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis

Here, we describe a new acoustic cryptanalysis key extraction attack,
applicable to GnuPG's current implementation of RSA. The attack can extract
full 4096-bit RSA decryption keys from laptop computers (of various
models), within an hour, using the sound generated by the computer during
the decryption of some chosen ciphertexts. We experimentally demonstrate
that such attacks can be carried out, using either a plain mobile phone
placed next to the computer, or a more sensitive microphone placed 4 meters
away.

http://www.cs.tau.ac.il/~tromer/acoustic/