Skipjack is the secret key encryption algorithm designed by the National Security Agency, and is used in the Clipper chip and Fortezza PC card. It was implemented in tamper-resistant hardware and its structure had been classified since its introduction in 1993. Skipjack was unclassified on June 24, 1998.
Skipjack is an 80-bit key, 64-bit block cipher.
BONUS
The C file, _skipjack.c, is a standalone Skipjack implementation. To compile it, type:
gcc -Wall _skipjack.c
A new binary, a.out, will be created.
To run the binary, type:
./a.out
COPYRIGHT AND LICENSE
Copyright (C) 2003 Julius C. Duque <jcduque (AT) lycos (DOT) com>
This library is free software; you can redistribute it and/or modify it under the same terms as the GNU General Public License.