kthreadd writes: In their research paper titled RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis Daniel Genkin, Adi Shamir and Eran Tromer et. all. present a method for extracting decryption keys from the GnuPG security suite using an interesting side-channel attack. By analysing the acoustic sound made by the CPU they were able to extract a 4096 bit RSA key in about an hour. A modern mobile phone placed next to the computer is sufficient to carry out the attack, but up to four meters have been successfully tested using specially designed microphones.