On Mon, Nov 19, 2001 at 04:06:06PM +1100, Brett Handley wrote: > I hope this isn't a silly question. > > Can the result of checksum/secure be used like a GUID, is it guaranteed to > be unique?
No, hashing is a many-to-one operation, mapping from an infinite space (arbitrarily long string series) to a finite space (string series of length 20), so there always has to be the chance of collisions. The chance of a collision is very small though, especially if you deal with a small number of values, say, less than a billion billion billion :-). For any two arbitrary strings to have the same checksum the chance is 1/(2^160). For at least one collision among n strings the chance is n/(2^160) (for n <= 2^160, obviously). -- Holger Kruse [EMAIL PROTECTED] -- To unsubscribe from this list, please send an email to [EMAIL PROTECTED] with "unsubscribe" in the subject, without the quotes.
