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Subject: Re: Use of MD5 as row keys - is this safe?
From: Joe Pallas <pallas@cs.stanford.edu>
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Date: Fri, 20 Jul 2012 13:35:10 -0700
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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=92t 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-algori=
thm-is-best-for-uniqueness-and-speed/145633#145633>.

Hope this helps,
joe