E2 (cipher)

Infobox block cipher
name = E2
designers = NTT
publish date = 1998
derived from =
derived to = Camellia
related to =
key size = 128, 192, or 256 bits
block size = 128 bits
structure = Feistel network
rounds = 12
cryptanalysis = Truncated differential cryptanalysis of 8 rounds without input or output transformations

In cryptography, E2 is a block cipher which was created in 1998 by NTT and submitted to the AES competition.

Like other AES candidates, E2 operates on blocks of 128 bits, using a key of 128, 192, or 256 bits. It uses a 12-round Feistel network. E2 has an input transformation and output transformation that both use modular multiplication, but the round function itself consists only of XORs and S-box lookups. The single 8×8-bit S-box is constructed from the composition of an affine transformation with the discrete exponentiation x¹²⁷ over the finite field GF(2⁸). NTT adopted many of E2's special characteristics in Camellia, which has essentially replaced E2.

There has been no published cryptanalysis of the full E2, but removing the input and output transformations and reducing to 8 rounds leaves a variant that is vulnerable to truncated differential cryptanalysis.

References

* cite conference
author = M. Matsui, T. Tokita
title = Cryptanalysis of a Reduced Version of the Block Cipher E2
booktitle = 6th International Workshop on Fast Software Encryption (FSE 1999)
pages = pp.71–80
publisher = Springer-Verlag
date = March 1999
location = Rome
url = http://www.mathmagic.cn/Crypt1998-2003/bibs/1636/16360071.htm
format = PDF
accessdate = 2007-02-27