The US Army's Field Manual on Basic Cryptanalysis (FM 34-40-2), dated September 1990 is available for downloading as an Acrobat PDF file from: http://www.atsc-army.org/cgi-win/$atdl.exe/fm/34-40-2/default.htm Fairly classic in nature (substitution, transposition, and code systems). Huge files (so far, at 28.8, after about an hour and a half, I've only been able to grab the table of contents and a couple of appendices - some kind-hearted person with a T1 or greater may want to get everything, then zip and mirror to save us bandwidth challenged folks the pain). Also, for the complete listings of almost 300 downloadable FMs through the Army's Digital Training Library (ATDL), check out: http://www.atsc-army.org/cgi-win/$atdl.exe?type=fm&header=%2Fatdl%2Fbrowse%2 Ffm.htm Have fun! Joel Note: This site isn't wholly reliable. It seems to regularly go up and down, and sometimes the bandwidth is terrible. Probably worth your patience though.