PGP RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis (2013)

PGP RSA Key Extraction via Low-Bandwidth Acoustic Cryptanalysis (2013)

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: they can convey information about the software running on the computer, and in particular leak sensitive information about security-related computations. In a preliminary presentation (Eurocrypt'04 rump session), we have shown that different RSA keys induce different sound patterns, but it was not clear how to extract individual key bits. The main problem was that the acoustic side channel has a very low bandwidth (under 20kHz using common microphones, and a few hundred kHz using ultrasound microphones), many orders of magnitude below the GHz-scale clock rates of the attacked computers.

In this paper 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 cipher-texts. 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.

comment: This merely confirms what I have been telling you before: Never put secret information onto an electronic device. Use paper and pencil only, but bear in mind that special forms of paper and pencils do exist containing electronic devices capable of recording your activity - believe it or not. And when writing always use a hard surface such as a glass plate and thoroughly wipe the surface after use. In this age you cannot be paranoid enough.

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