Re: [HACKERS] Patch for UUID datatype (beta)
От | Jeff Davis |
---|---|
Тема | Re: [HACKERS] Patch for UUID datatype (beta) |
Дата | |
Msg-id | 1158615504.30652.15.camel@dogma.v10.wvs обсуждение исходный текст |
Ответ на | Re: [HACKERS] Patch for UUID datatype (beta) ("Jim C. Nasby" <jimn@enterprisedb.com>) |
Список | pgsql-patches |
On Mon, 2006-09-18 at 16:00 -0500, Jim C. Nasby wrote: > BTW, at a former company we used SHA1s to identify files that had been > uploaded. We were wondering on the odds of 2 different files hashing to > the same value and found some statistical comparisons of probabilities. > I don't recall the details, but the odds of duplicating a SHA1 (1 in > 2^160) are so insanely small that it's hard to find anything in the > physical world that compares. To duplicate random 256^256 numbers you'd > probably have to search until the heat-death of the universe. That assumes you have good random data. Usually there is some kind of tradeoff between the randomness and the performance. If you read /dev/random each time, that eliminates some applications that need to generate UUIDs very quickly. If you use pseudorandom data, you are vulnerable in the case a clock is set back or the data repeats. Regards, Jeff Davis
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