Tim Dierks <[EMAIL PROTECTED]> writes: > 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've thought that. Unfortunately, I don't know that there are good block ciphers out there with 32 bit block sizes, and some uses (for example, IP fragment ids) are 32 bits. > 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. Perhaps -- I don't know of a good one. -- Perry E. Metzger [EMAIL PROTECTED] --------------------------------------------------------------------- The Cryptography Mailing List Unsubscribe by sending "unsubscribe cryptography" to [EMAIL PROTECTED]
