SERPENT – A Candidate Block Cipher for the Advanced Encryption Standard "Serpent is now completely in the public domain, and we impose no restrictions on its use. This was announced on the 21st August at the First AES Candidate Conference. The optimised implementations in the submission package are now under the General Public License (GPL), although some comments in the code still say otherwise. You are welcome to use Serpent for any application. If you do use it, we would appreciate it if you would let us know!" (1999)
Bruce Schneier; John Kelsey; Doug Whiting; David Wagner; Chris Hall. Niels Fergusonk; Tadayoshi Kohno; Mike Stay (2000). "The Twofish Team's Final Comments on AES Selection"(PDF). Archived from the original(PDF) on 2 January 2010. Retrieved 19 January 2015.
Kohno, Tadayoshi; Kelsey, John; Schneier, Bruce (2000). "Preliminary Cryptanalysis of Reduced-Round Serpent". The Third Advanced Encryption Standard Candidate Conference, April 13–14, 2000, New York, New York, USA. National Institute of Standards and Technology. pp. 195–211.
Bruce Schneier; John Kelsey; Doug Whiting; David Wagner; Chris Hall. Niels Fergusonk; Tadayoshi Kohno; Mike Stay (2000). "The Twofish Team's Final Comments on AES Selection"(PDF). Archived from the original(PDF) on 2 January 2010. Retrieved 19 January 2015.