Twofish is a block cipher by Counterpane Labs, published in 1998. It was one of the five Advanced Encryption Standard (AES) finalists, and was not selected as AES.
Twofish has a 128-bit block size, a key size ranging from 128 to 256 bits, and is optimized for 32-bit CPUs. Currently there is no successful cryptanalysis of Twofish.
Twofish is unpatented, and the source code is uncopyrighted and license-free; it is free for all uses.
The designers of Twofish offered $10,000 in prize money for the best attack on Twofish during the first round of the AES evaluation. Congratulations to Fauzan Mirza and Sean Murphy, who won the contest for their paper "An Observation on the Key Schedule of Twofish."
Pawel Chodowiec and Kris Gaj have written a paper on implementing Twofish using FPGA devices.
The magazine News/400 ran an article on Twofish encryption on the AS/400.
The best analysis of Twofish is by Shiho Moriai and Yiquin Lisa Yin, and was published in Japan in 2000.
Twofish was created and analyzed by:
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