3 ms·

Version 4 UUIDs pretty much have to be generated from reasonable(-ish) CSRNG. The assumption that the resulting 122bits are universally unique requires that the

by dfox 8y ago

Version 4 UUIDs pretty much have to be generated from reasonable(-ish) CSRNG. The assumption that the resulting 122bits are universally unique requires that they are truly chosen at random, CS(P)RNG is the most sane way to accomplish that.

dragontamer 8y ago
> The assumption that the resulting 122bits are universally unique requires that they are truly chosen at random, CS(P)RNG is the most sane way to accomplish that. Certainly not. Take a Version 1 UUID (time-based), and spin it through a 128-bit LCGRNG. Do the AND / OR bitmasks needed to properly tag it a Version4 UUID and you're done. Bam, universally unique but not cryptographically random. This would be very fast (cryptographic entropy is very slow!), and would be ideal for databases or most purposes.