GDES

Infobox block cipher
name = GDES
designers = Ingrid Schaumuller-Bichl
publish date = 1981
derived from = DES
derived to =
related to =
key size =
block size = variable, multiple of 32
structure = generalized Feistel network
rounds = variable, even
cryptanalysis = differential cryptanalysis breaks most variants more easily than DESIn cryptography, the Generalized DES Scheme (GDES or G-DES) is a variant of the DES block cipher designed to speed-up the encryption while improving its security. The scheme was proposed by Ingrid Schaumuller-Bichl in 1981.

GDES generalizes the Feistel network structure of DES to larger block sizes. In each round, the DES round function is applied to the rightmost 32-bit subblock, and the result is XORed with all the other parts. Then the block is rotated 32 bits to the right.

In 1990, Eli Biham and Adi Shamir showed that GDES was vulnerable to differential cryptanalysis, and that any GDES variant faster than DES is also less secure than DES.

References

* Eli Biham, Adi Shamir: Differential Cryptanalysis of DES-like Cryptosystems. CRYPTO 1990: 2-21
* Ingrid Schaumuller-Bichl, Zur Analyse des Data Encryption Standard und Synthese Verwandter Chiffriersysteme, Ph.D. Thesis, Linz university, May 1981. (In German).
* I. Schaumuller-Bichl, "On the Design and Analysis of New Cipher Systems Related to DES," Technical Report, Linz University, 1983.
* cite book
last = Schneier
first = Bruce
authorlink = Bruce Schneier
title = Applied Cryptography, Second Edition
publisher = John Wiley & Sons
date = 1996
pages = 296
id = ISBN 0-471-11709-9