[填空题]Clattering keyboards may seem the white noise of the modern age, but they betray more information than unwary typists realize. Simply by analyzing audio recordings of keyboard clatter, computer scientists can now reconstruct an accurate transcript of what was typed--including passwords. (41) .
Such snooping is possible because each key produces a characteristic dick, shaped by its position on the keyboard, the vigor and hand position of the typist, and the type of keyboard used. But past attempts to decipher keyboard sounds were only modestly successful, requiring a training session in which the computer matched a known transcript to an audio recording of each key being struck. (42) . Furthermore, each new typist or keyboard required a fresh transcript and training session, limiting the method’s appeal to would-be hackers.
Now, in a blow to acoustic security, Doug Tygar and his colleagues at the University of California, Berkeley, have published details o