LEX is a stream cipher

Stream cipher

In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream . In a stream cipher the plaintext digits are encrypted one at a time, and the transformation of successive digits varies during the encryption...

 based on the round transformation of AES

Advanced Encryption Standard

Advanced Encryption Standard is a specification for the encryption of electronic data. It has been adopted by the U.S. government and is now used worldwide. It supersedes DES...

. LEX provides the same key agility and short message block performance as AES while handling longer messages faster than AES. In addition, it has the same hardware and software flexibility as AES, and hardware implementations of LEX can share resources with AES implementations.

Designed by Alex Biryukov

Alex Biryukov

Alex Biryukov is a cryptographer, currently an assistant professor at the University of Luxembourg. His notable work includes the design of the stream cipher LEX, as well as the cryptanalysis of numerous cryptographic primitives. In 1998, he developed impossible differential cryptanalysis together...

, LEX is a Phase 2 Focus candidate for the eSTREAM

ESTREAM

eSTREAM is a project to "identify new stream ciphers suitable for widespread adoption", organised by the EU ECRYPT network. It was set up as a result of the failure of all six stream ciphers submitted to the NESSIE project. The call for primitives was first issued in November 2004. The project was...

 project. It is not patented.

A new revision of LEX protects against a slide attack

Slide attack

The slide attack is a form of cryptanalysis designed to deal with the prevailing idea that even weak ciphers can become very strong by increasing the number of rounds, which can ward off a differential attack. The slide attack works in such a way as to make the number of rounds in a cipher irrelevant...

found in an earlier version.

External links

• eSTREAM page on LEX