On Sat, 6 Sep 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 (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. >
Why does it need to be strictly non repeating? Is 2^n always large enough that sequences of length > 2^n are uninteresting? If sequences longer than 2^n are practical and *every* subsequence of 2^n elements is free of duplicates the entire thing is periodic, this may or may not be a problem... -- Viktor. --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]