Computer scientist and cryptographer.
With Jim Reeds founder of the Voynich Manuscript Mailing List in 1991.
Notable for being the first person to publicly solve parts 1-3 on the CIA's (Wikipedia page Kryptos sculpture refers) in 1999. Also debunked the Beale Ciphers.
His page on Wikipedia, including a list of his writings, is  and on chess Programming Wiki 
A list of his publications here  and here .