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The following archive was created by hippie-mail 7.98617-22 on Sat Apr 10 1999 - 01:13:58
Martin Grap (mgrap@concord-eracom.de)
Wed, 2 Sep 1998 09:19:33 +0100
At 03:16 PM 9/1/98 +0100, you wrote:
>
>On Mon, 31 Aug 1998, Sandy Harris wrote:
>
>> I've thought up a method of cryptanalysis which I don't recall
>> reading of anywhere, probably for several of the following reasons:
>>
>> it's pretty obvious
>> it's hopelessly inefficient
>> my memory's not all that good
>> I haven't read all that much
>>
>> But it looks to me like it isn't entirely hopeless, & even if it
>> is, then proving it hopeless for a given cipher might be useful.
>
>I've been thinking about it for a long time. Glad to know I'm
>not the only insane person around :-)
>
If I remeber correctly, Shannon discussed this sort of algebraic
cryptanalysis in his 1949 paper "A Communications Theory of Secrecy
systems". As one possibility to thwart these attacks he recommends to
use components which add a lot of "confusion" to the cipher. I.e.
he recommends to use "complicated" non-linear mappings as building
blocks for the cipher (today mostly in form of S-Boxes). Other building
blocks should be used to "diffuse" the statistical properties of the
plaintext in such a way that an enemy needs a large amount of intercepted
material in order to be able to reconstruct these statistical properties.
In other words these building blocks add diffusion to the cipher (today
mostly in the form of permutations or special linear functions).
Horst Feistel based his work on block ciphers on Shannon's recommendations
and therefore it can be expected that most modern blockciphers are immune
to this sort of analytical attack. But one never knows for sure .... :-)
Martin
--------
Martin Grap, Concord-Eracom Computer Security GmbH
Talstrasse 11, D-72218 Wildberg, Germany
Tel. : {+49} (0)7054-9267-0, Fax: {+49} (0)7054-1837
e-mail: mgrap@concord-eracom.de, CE-homepage: http://www.concord-eracom.de
The following archive was created by hippie-mail 7.98617-22 on Sat Apr 10 1999 - 01:13:58