Full level of detail about Twofish encryption code which was one of the 5 finalists (but not the winner) of the AES. There is an interesting set of links to numerous packages using Twofish for encryption (because it is free I guess!), including TreePad.

Schneier is also the author of the new book “Beyond Fear: Thinking Sensibly About Security in an Uncertain World” from September 2003.

[1] Schneier.com: Twofish: “Twofish: A New Block Cipher

Twofish is a block cipher by Counterpane Labs. It was one of the five Advanced Encryption Standard (AES) finalists. Twofish is unpatented, and the source code is uncopyrighted and license-free; it is free for all uses. “