On Sat, Dec 7, 2013 at 3:24 AM, John Young <jya@pipeline.com> wrote:

Contact mics for acquiring vibration and resonance emanations are among the still classified TEMPEST offensive and defensive activities,

interesting work on using poor quality sound (like from a phone) for chosen cipher text attacks with key recovery for GPG. also note that they use frequencies >10kHz. as discussed in the high frequency audio covert channel, this range is fairly contention free and easily accessible to microphones in consumer electronics of various types. http://www.cs.tau.ac.il/~tromer/acoustic/ """ 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. Beyond acoustics, we demonstrate that a similar low-bandwidth attack can be performed by measuring the electric potential of a computer chassis. A suitably-equipped attacker need merely touch the target computer with his bare hand, or get the required leakage information from the ground wires at the remote end of VGA, USB or Ethernet cables. """