What is Twofish?
Q: What is Twofish?
A: Twofish is a symmetric key block cipher with a block size of 128 bits and key lengths up to 256 bits.
Q: How was Twofish related to the earlier block cipher Blowfish?
A: Twofish's main features are the use of pre-computed key-dependent S-boxes, and a relatively complex key schedule. One half of an n-bit key is used as the actual encryption key and the other half of the n-bit key is used to modify the encryption algorithm (key-dependent S-boxes).
Q: Was Twofish chosen as an Advanced Encryption Standard?
A: No, in 1997, NIST announced for competition to choose a successor to DES which would be known as AES, however Twofish was not selected as a standard.
Q: What elements does Twofish use from other designs?
A: Twofish uses some elements from other designs; for example, the pseudo-Hadamard transform (PHT) from the SAFER family of ciphers.
Q: Does it use Feistel structure like DES?
A: Yes, it does use Feistel structure like DES.
Q: Is it faster than Rijndael for 128 bit keys?
A: On most software platforms, Twofish is slightly slower than Rijndael for 128 bit keys.
Q: Is it faster than Rijndael for 256 bit keys?
A: It is somewhat faster than Rijndael for 256 bit keys.
