Giles Bowkett writes:

http://www.cryptography.com/timingattack.html

and found the whole thing to be totally incomprehensible from a layman's point of view. I apologize for having not read "Applied Cryptography", which might have made the abstract a simpler read - but even if I had I'd have been baffled by a lot of the terminology and equations in this paper.

If you had read and understood Applied Cryptography you would understand the paper. I'm sorry, but to paraphrase a smarter man than I, there is no royal road to cryptography. You have to study it. The only thing that can be said to a layman is that different keys will require different amounts of times to deal with different texts in certain public key systems, so by timing how long it takes to perform operations you can get information about the keys. Perry