Twofish is a symmetric key block cipher designed by Bruce Schneier and his team in the late 1990s. It operates on 128-bit blocks and supports key sizes of 128, 192, and 256 bits. Twofish is known for its speed and security, making it suitable for various applications, including encryption in software and hardware. As a finalist in the Advanced Encryption Standard (AES) competition, Twofish is recognized for its robust design and resistance to cryptanalysis. It employs a Feistel network structure, which enhances its security by allowing complex transformations of the data during encryption and decryption processes.