Li Zhuang, Feng Zhou, and Doug Tygar have an interesting new paper showing that if you have an audio recording of somebody typing on an ordinary computer keyboard for fifteen minutes or so, you can figure out everything they typed.
Makes a lot of sense -- it's more or less just based upon basic cryptographic principles. Just identify the unique sound each key makes as it strikes, and then run a frequency analysis to determine what it is they're saying. [Via GeekPress
, which also links to the gallery of alternative keyboards