Ned Konz <ned at bike-nomad.com> said:
>So even if your random generator isn't too good, you can't possibly=20
>generate the same UUID as any other machine (unlike a scheme that=20
>just uses random numbers, or replaces the unique MAC address with a=20
>non-unique IP address).
>
Unless someone fiddles with the MAC address. And of course, because you devote
a large part (6 out of 16 bytes) to the MAC address, the random number space
decreases drastically increasing the chance that you'll generate a dupe on the
same box (I said 2^128 elsewhere which would make it 2^80, but actually this
is a collision-type thingie so the chance is way larger; don't have Applied
Cryptography around and I forgot how much larger, but IIRC the chance of a
collision in 80 bits gets into the realm of 'this will happen in the course of
time' ;-)). 

(note that because it is impossible to find a machine's MAC or IP address, the
whole concept doesn't exist - a MAC or IP address is bound to the interface,
not the machine - it is always the administrator's responsibility to manually
configure a unique MAC or IP address into the UUID generator; IMHO there's not
much difference between either, IP addresses just eat 2 bytes less which you
can apply in other UUID fields).

-- 
Cees de Groot               http://www.cdegroot.com     <cg at cdegroot.com>
GnuPG 1024D/E0989E8B 0016 F679 F38D 5946 4ECD  1986 F303 937F E098 9E8B
Cogito ergo evigilo