2001-05-17

Steak

Steak is a two-way error propagating cipher that employs the full potential of Propagating Cipher Feedback (PCFB) stream encryption. Due to its dedication to the PCFB mode, it is much faster than any conventional block cipher run in PCFB mode.

The purpose of PCFB mode stream encryption is to make it possible to detect cipher text errors as soon as possible, simply by observing that all decrypted text past the occurence of an error will be complete garbage. There is no need to hash and sign transmission packets in order to verify integrity and authenticity. This means that the speed of streamed transmissions is multiplied. 

The technology of PCFB stream encryption was invented by Henrick Hellström in 1998 along with an early PCFB stream cipher prototype called WeakCipher. The PCFB mode might be described as a derivate of CFB-8/n mode, where the feedback buffer cipher text is passed to the next round and the feedback buffer plain text is discarded, instead of the other way around. 

StreamSec has recently updated the reference implementation of Steak. The new reference implementation is refered to as Steak2 and is available here:

View Steak2 source code (html format)
Download Steak2 source code (Delphi source file)
Download Steak2 specification (PDF format)