[19342] in cryptography@c2.net mail archive
Re: another feature RNGs could provide
daemon@ATHENA.MIT.EDU (Ben Laurie)
Wed Dec 21 13:42:51 2005
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Wed, 21 Dec 2005 06:10:41 +0000
From: Ben Laurie <ben@algroup.co.uk>
To: cryptography@metzdowd.com
In-Reply-To: <20051212155423.GL30846@randombit.net>
Jack Lloyd wrote:
> On Mon, Dec 12, 2005 at 12:20:26AM -0600, Travis H. wrote:
>> 2) While CTR mode with a random key is sufficient for creating a
>> permutation of N-bit blocks for a fixed N, is there a general-purpose
>> way to create a N-bit permutation, where N is a variable? How about
>> picking a cryptographically strong permutation on N elements, where N
>> is not necessarily a power of 2?
>
> Use can use the Bear or Lion constructions to form 2^{arbitrary} bit block
> ciphers quite easily.
Good ciphers aren't permutations, though, are they? Because if they
were, they'd be groups, and that would be bad.
--
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** ApacheCon - Dec 10-14th - San Diego - http://apachecon.com/ **
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