On Tue, Dec 03, 2002 at 02:27:02AM -0500, Thor Lancelot Simon wrote:
> I'm curious how you decided that the likelihood of a random collision was
> too great with a 32-bit sum.  I started to make some rather simplistic
> mathematical arguments here but after investigating the literature on
> CRC error rates for about an hour, all I'm really sure of is that my
> calculations were wrong.

FWIW, assuming I did the math right, according to the birthday paradox, 
there's a 50% probability of a collision in a pool of about 77162 
random 32-bit numbers. I.e., if you assigned a random 32-bit number to 
77162 files, there'd be a 50% chance that two files have the same 
number. For a 64-bit random number, the 50% chance of a collision 
occurs at around 5,056,937,540 numbers.

CRCs aren't uniformly distributed though, so this might not mean much :)
-- 
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