"John S. Denker" <[EMAIL PROTECTED]> writes: > 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.
I'd thought of that, but encrypting with a stream cipher would not work for this application -- it would not produce an ergodic sequence -- and encrypting with a block cipher would require that the block cipher use unusually small block sizes for many such applications. Perry --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]
