3 ms·

At one time, UUIDs were made by combining a fine timestamp with MAC-style hardware ids, giving a value that was conceptually unique in time and space. IIRC, it

by psyc 9y ago

At one time, UUIDs were made by combining a fine timestamp with MAC-style hardware ids, giving a value that was conceptually unique in time and space. IIRC, it was eventually realized that choosing a value at random (e.g. using true RNG) was just as good. 2^128 is about 300 undecillion. Roughly 800 billion values per nanosecond for the age of the universe.

pacaro 9y ago
Version 4 UUIDs are preferred not because random is as good, indeed for some usecases it is worse, but typically because leaking information about time of creation and MAC address of the creator is undesirable
- dannyw 9y ago
  Why not just hash it then?
  - dfox 9y ago
    Because the probability of random collision for hash function is same as probability of generating two colliding random bit strings of same length as the hash.