[14040] in cryptography@c2.net mail archive
Re: cryptographic ergodic sequence generators?
daemon@ATHENA.MIT.EDU (Tim Dierks)
Sat Sep 6 19:13:30 2003
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Date: Sat, 06 Sep 2003 14:33:56 -0400
To: cryptography@metzdowd.com
From: Tim Dierks <tim@dierks.org>
In-Reply-To: <87llt14wm9.fsf@snark.piermont.com>
At 02:09 PM 9/6/2003, Perry E. Metzger wrote:
>For making things like IP fragmentation ids and other similar protocol
>elements unpredictable, it would be useful to have what I'll call a
>cryptographic ergodic sequence generator -- that is, a generator that
>will produce a sequence of n bit numbers such that there are no
>repeats until you pass the 2^nth number in the sequence.
>
>Anyone know how to produce such a thing?
It seems to me that this could be constructed with a block cipher with a
block size n bits long by encrypting the values 0..2^n sequentially with a
random key.
I'm sure that it would be possible to design a Feistel-based block cipher
with variable block size, supporting some range of even values of n.
- Tim
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