Crypto Boffins - led by Adi Shamir of RSA fame - are investigating whether it might be possible to gain valuable clues about private encryption keys simply by listening to a targeted computer.

The sounds made by capacitors on motherboards might, in theory, give attackers code-breaking clues in much the same way electro-magnetic leakage or power fluctuations can be used in so-called "side-channel" attacks on secure systems. These kinds of attacks are well beyond the capability of your average hacker but they do have applications in the design of tamper-resistant systems. The research shows that cryptanalysts are prepared to think of any possible attack vector in their quest to ensure cryptographic systems remain secure.

Preliminary work (http://www.wisdom.weizmann.ac.il/~tromer/acoustic/) by Adi Shamir and Eran Tromer of the Weizmann Institute in Israel showed that "acoustic emanations from personal computers are a surprisingly rich source of information on CPU activity". For instance the researchers have found that RSA signature/decryption sounds different for different secret keys and that monitoring audio signals can reveal the time of a decryption operation, useful in timing attacks, especially when an attacker can affect that input data of a cryptographic operation. The audio signals of interest are well above the frequency generated by fans and thus easily filtered out. A proof-of-concept presentation on the research can be found here (http://www.wisdom.weizmann.ac.il/~tromer/acoustic/). ®

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