Xmx

Xmx

Infobox block cipher
name = xmx
designers = David M'Raïhi, David Naccache, Jacques Stern, Serge Vaudenay
publish date = January 1997
derived from =
derived to =
related to =
key size = variable, equal to block size
block size = variable
structure =
rounds = variable, even
cryptanalysis = differential cryptanalysis, complementation property, weak keys
In cryptography, xmx is a block cipher designed in 1997 by DavidM'Raïhi, David Naccache, Jacques Stern, and Serge Vaudenay. According to thedesigners it "uses public-key-like operations as confusion and diffusion means." Thecipher was designed for efficiency, and the only operations it uses are XORsand modular multiplications.

The main parameters of xmx are variable, including the
block size and key size, which are equal, as wellas the number of rounds. In addition to the key, it also makesuse of an odd modulus "n" which is small enough to fit in a single block.

The round function is f(m)=(moa)·b mod n, where a and b aresubkeys and b is coprime to n. Here moa represents an operation thatequals m XOR a if that is less than n, and otherwise equals m. This is a simpleinvertible operation: moaoa = m. The xmx cipher consistsof an even number of iterations of the round function, followed by a final owith an additional subkey.

The key schedule is very simple, using the same key for all the multipliers, andthree different subkeys for the others: the key itself for the first half of thecipher, its multiplicative inverse mod n for the last half, and the XOR of these twofor the middle subkey.

The designers defined four specific variants of xmx:
* "Standard": 512-bit block size, 8 rounds, n=2512-1
* "High security": 768-bit block size, 12 rounds, n=2768-1
* "Very-high security": 1024-bit block size, 16 rounds, n=21024-1
* "Challenge": 256-bit block size, 8 rounds, n=(280-1)·2176+157

Borisov, et al, using a multiplicative form of differential cryptanalysis, found acomplementation property for any variant of xmx, like the first three above, such thatn=2k-1, where k is the block size. They also found large weak key classesfor the Challenge variant, and for many other moduli.

References

* cite conference
author = David M'Raïhi, David Naccache, Jacques Stern, Serge Vaudenay
title = xmx: A Firmware-Oriented Block Cipher Based on Modular Multiplications
booktitle = 4th International Workshop on Fast Software Encryption (FSE '97)
pages = pp.166–171
publisher = Springer-Verlag
date = January 1997
location = Haifa
url = http://citeseer.ist.psu.edu/19207.html
format = PDF/PostScript
accessdate = 2007-01-03

* cite conference
author = Nikita Borisov, Monica Chew, Rob Johnson, David Wagner
title = Multiplicative Differentials
booktitle = 9th International Workshop on Fast Software Encryption (FSE '02)
pages = pp.17–33
publisher = Springer-Verlag
date = February 2002
location = Leuven
url = http://citeseer.ist.psu.edu/672650.html
format = PDF/PostScript
accessdate = 2007-01-03


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • XMX (XM) — Infobox Radio Station name = XMX area = United States Canada slogan = airdate = 2007 08 01 frequency = XM 2 format = XM Featured Shows owner = XM Satellite Radio class = Satellite Radio Station website =… …   Wikipedia

  • XMX — Xtreme Motocross (Community » Sports) ** X Protocol Multiplexer (Computing » Software) ** X Window System session on multiple X displays (Computing » Software) * Xtreme MotoX (Community » Sports) * Autodesk AutoCAD External Message Compiled File… …   Abbreviations dictionary

  • xmx — ISO 639 3 Code of Language ISO 639 2/B Code : ISO 639 2/T Code : ISO 639 1 Code : Scope : Individual Language Type : Living Language Name : Maden …   Names of Languages ISO 639-3

  • XMX — abbr. X protocol Multiplexer …   Dictionary of abbreviations

  • XM Live — Infobox Radio Station name = XM Live area = Off air airdate = September 2001 frequency = XM120 class = Satellite Radio Station format = Multipurpose, Special Events owner = XM Satellite Radio website = [http://www.xmradio.com/programming/channel… …   Wikipedia

  • Theme Time Radio Hour — Infobox Radio Show show name = Theme Time Radio Hour format = Music show runtime = 1 hour per episode, weekly creator = Bob Dylan Eddie Gorodetsky writer = executive producer = Lee Abrams starring = Bob Dylan Pierre Mancini (announcer) opentheme …   Wikipedia

  • Block cipher — In cryptography, a block cipher is a symmetric key cipher operating on fixed length groups of bits, called blocks, with an unvarying transformation. A block cipher encryption algorithm might take (for example) a 128 bit block of plaintext as… …   Wikipedia

  • Data Encryption Standard — The Feistel function (F function) of DES General Designers IBM First publis …   Wikipedia

  • Differential cryptanalysis — is a general form of cryptanalysis applicable primarily to block ciphers, but also to stream ciphers and cryptographic hash functions. In the broadest sense, it is the study of how differences in an input can affect the resultant difference at… …   Wikipedia

  • International Data Encryption Algorithm — IDEA An encryption round of IDEA General Designers Xuejia Lai and James Massey …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”