[14039] in cryptography@c2.net mail archive
Re: cryptographic ergodic sequence generators?
daemon@ATHENA.MIT.EDU (John S. Denker)
Sat Sep 6 19:12:46 2003
X-Original-To: cryptography@metzdowd.com
X-Original-To: cryptography@metzdowd.com
Date: Sat, 06 Sep 2003 14:30:36 -0400
From: "John S. Denker" <jsd@av8n.com>
To: cryptography@metzdowd.com
In-Reply-To: <87llt14wm9.fsf@snark.piermont.com>
On 09/06/2003 02:09 PM, 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
> (that is, the sequence is a permutation of all 2^n bit numbers) and
> such that it is very difficult to predict what the next number in the
> sequence might be beyond the fact that it will not be one of the
> numbers seen earlier in the sequence. It is also rather important
> that the generator be computationally inexpensive.
>
> Anyone know how to produce such a thing?
Encrypted counter.
The counter provably has a cycle of 2^n.
The encryption is provably 1-to-1.
Choose the encryption key randomly and keep it secret.
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