Solitaire is an encryption system based on a deck of cards by Bruce
Schneier.  Although it is designed to be worked out by a human, it can
work on computers.  This is the reference implementation programmed in
Perl.  The program itself is installed as 'solitaire', and the source
code and test vectors are installed in share/doc/solitaire.

Please read the web site below before relying on this for real security.