Twofish Algorithm

Twofish is a symmetric block cipher operating on 128 bit blocks with keys up to 256 bits, combining a Feistel network structure with key-dependent S-boxes, a pseudo-Hadamard transform and a complex key schedule to resist a wide range of cryptanalytic attacks. It was designed by a team including Bruce Schneier as an entrant in the United States National Institute of Standards and Technology's competition to select the Advanced Encryption Standard, and it was one of five finalists, ultimately losing to Rijndael. It remains free to use with no licensing restrictions and continues to see use in some encryption software.