# Twofish

Known 251 chosen plaintexts.

Twofish is a symmetric encryption algorithm in computer science, which was developed by Bruce Schneier, Niels Ferguson, John Kelsey, Doug Whiting, David Wagner and Chris Hall. It is a block cipher with a block size of 128 bits and 16 rounds, the key lengths are 128, 192 or 256 bits.

## AES Application

Twofish represents the successor of Blowfish and stood in 1998/1999 the Retiring to the Advanced Encryption Standard. There he met with the algorithms MARS, RC6, Rijndael and Serpent in the round of the last five.

In Twofish were regarding its safety, especially the properties of the key - sharing and its complexity, which affects a security analysis criticized. On the other hand, Twofish, according to its developer team just by sharing this key (key -dependent S- boxes ) a security architecture against unknown attacks dar.

## License

Twofish is not patented and published under Public Domain. It is thus to use any freely available.

### Sample Applications

The Twofish algorithm is implemented, among others, the following open source software packages:

- FreeOTFE - disk encryption
- GNU Privacy Guard - encrypt and sign files and e- mails
- TrueCrypt - Disk Encryption, encryption of partitions and container files
- KeePass - password manager
- CrossCrypt - disk encryption
- DiskCryptor - disk encryption
- Dm -crypt - disk encryption

## Cryptanalysis

The previous best published attack possibility in the form of a Distinguishing Attack is the limited differential analysis by Moriai & Yin. The document describes that the probability for a limited differentials 2-57.3 is per block and that it takes approximately 251 chosen plaintexts ( about 32 PiB data) to find a usable pair of limited differentials and thereby distinguish the cipher from a random number sequence can be.

Bruce Schneier responded in a 2005 blog post that the document does not present a complete cryptanalysis, but only some characteristic hypotheses of differential analysis. This would mean in practical terms that Twofish was not broken in the slightest. The authors of the published 2000 analysis have since released no new information.