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New acoustic attack steals data from keystrokes with 95% accuracy
(www.bleepingcomputer.com)
This is a most excellent place for technology news and articles.
Hard to do, but with a very standard keyboard like a Mac keyboard the resonance signatures should be slightly different based on location on the board, take into account pattern recognition, relative pause length between keystrokes, and perhaps some forced training ( ie. Get them to type know words like a name and address to feed algorithm) I think it's potentially possible.