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Re: Collections
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From:
Dave Mitchell
Date:
October 1, 2002 01:19
Subject:
Re: Collections
Message ID:
20021001091732.A5026@fdgroup.com
On Mon, Sep 30, 2002 at 04:41:30PM -0700, Brent Dax wrote:
> 'Brian Ingerson':
> # then you call the internal HASH (storable->md5 or
>
> I have one more concern. I don't know the details of MD5, so I don't
> know how remote this possibility is, but what if two different data
> structures MD5 out the same? Like I said, I don't know much about MD5,
> but it would seem to me that any time you reduce a ton of arbitrary
> strings to thirty-two hexits, you'll get a collision at least once or
> twice.
MD5 is intended to be a cyptographically strong hash function - ie
digital signatures etc rely on the improbability of being able to
engineer a collision.
Assuming your program maintained a million-key hash, and updated the hash
a million times per second, you might expect a collision once every
10,000,000,000,000,000,000 years or so. If you're worried, use
SHA, which would increase that to 1E38 years or so.
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