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From Joe Pallas <pal...@cs.stanford.edu>
Subject Re: Use of MD5 as row keys - is this safe?
Date Fri, 20 Jul 2012 20:35:10 GMT

On Jul 20, 2012, at 12:16 PM, Michel Segel wrote:

> I don't believe that there has been any reports of collisions, but if. You are concerned
you could use the SHA-1 for generating the hash. Relatively speaking, SHA-1is slower, but
still fast enough for most applications.

Every hash function can have collisions, by definition.  If the correctness of your design
depends on collisions being impossible, rather than very rare, then your design is faulty.

Cryptographic hash functions have the property that it is computationally hard to create inputs
that match a given output.  That doesn’t in itself make cryptographic hash functions better
than other hash functions for avoiding hot-spotting.  (But it does usually make cryptographic
hash functions more expensive to compute than other hash functions.)

You may want to look at <http://www.strchr.com/hash_functions>  and <http://programmers.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed/145633#145633>.

Hope this helps,

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