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ABC Stream Cipher

ABC stream cipher architecture

ABC Stream Cipher Architecture

ABC is a synchronous stream cipher optimized for software applications. Its design offers large flexibility concerning key material usage and memory consumption. A version of ABC with a 128-bit key and 32-bit internal variables was submitted to eSTREAM project.

Current state

The current version of the ABC stream cipher is ABC v.3. It fixes the weaknesses of the previous versions, however, not all of them. A number of weak keys still exists for ABC v.3. This issue is currently under investigation. See Phase 1 and Phase 2 ABC pages at eSTREAM for a list of papers on ABC.


A new approach to the stream cipher design is used in ABC development which results in a cipher based upon key- and clock-dependent state transition and filter functions. Our techniques guarantee the period of 232·(2127-1) words (the longest of possible), uniform distribution, and high linear complexity of the keystream of ABC.


ABC can be efficiently implemented in software. Our ANSI C implementation provides the throughput of about 7 Gbps on a standard 3.2 GHz Pentium 4 processor. The flexibility property enables its efficient application on almost every platform by choosing proper implementation parameters.

Legal Notice

The ABC stream cipher is Copyright (C) 2005-2006 Vladimir Anashin, Andrey Bogdanov, Ilya Kizhvatov.

The authors allow free usage of the ABC stream cipher design for any non-commercial or commercial purposes provided each of the following holds:

  1. The original ABC stream cipher design is not modified in any way.
  2. The name "ABC stream cipher" is clearly specified.
  3. The names of the ABC stream cipher inventors (Vladimir Anashin, Andrey Bogdanov, Ilya Kizhvatov) are clearly specified.

ABC reference implementation is provided "as is" without any express or implied warranty. The authors are not in any way liable for any use of this software.

Last updated 2007-06-21
© 2005-2007 Vladimir Anashin, Andrey Bogdanov and Ilya Kizhvatov