E2 is a block cipher from Nippon Telephone and Telegraph. It was candidate in the AES competition but did not make it into the finals. Like all AES candidates, it uses 128-bit blocks and supports key sizes of 128, 192 or 256 bits. It is a 12-round Feistel network using a single 8 by 8 S-box.
There has been no published cryptanalysis of the full E2, but there is an attack on a reduced-round version .
Camellia shares some design features with E2 and has largely replaced it.
- Mitsuru Matsui, Toshio Tokita (March 1999), Cryptanalysis of a Reduced Version of the Block Cipher E2, Springer-Verlag, at 71-80