FOX (cipher)

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IDEA NXT (FOX)

Image:Foxround.png

Round function for NXT128

General

Designer(s)

Pascal Junod, Serge Vaudenay

First published

2003

Derived from

IDEA

Cipher(s) based on this design

None

Algorithm detail

Block size(s)

64, 128 bits

Key size(s)

0-256 bits

Structure

Lai-Massey scheme

Number of rounds

Best cryptanalysis

External cryptanalysis conducted by David Wagner and Jacques Stern. No attacks known as of August 2005.

In cryptography, the FOX (now called IDEA NXT) algorithm is a block cipher designed by Pascal Junod and Serge Vaudenay of EPFL (Lausanne, Switzerland). It was conceived between 2001 and 2003, the project was originally named FOX and was published in 2003. In May 2005 it was announced by MediaCrypt under the name IDEA NXT. IDEA NXT is the successor of the IDEA algorithm and it uses an extended Lai-Massey scheme known for its robustness to cryptanalysis. It was mandated by MediaCrypt, a Swiss company owner of the distribution rights on IDEA and the patents of IDEA NXT. The IDEA NXT cipher is a family of different sub-ciphers with various blocks and keys size : Standard NXT64 (block of 64 bits, key of 128 bits, 12 rounds) and Standard NXT128 (block of 128 bits, key of 256 bits, 12 rounds). Variations of the Standard versions can be built (key of 0-256 bits, round numbers from 2-255). Also individual tables (sbox, permutation matrix) can be loaded, replacing the Standard table.