Cryptographic hash uniquness (was [Haskell-cafe] Simple network client)

Lanny Ripple lanny at
Thu Jan 31 13:09:29 EST 2008

Depending on which hash you use you can get upwards of "document 
hask keys won't collide before the heat-death of the universe".

There is of course a lot more to it than that.  Google around 
about hashing, cryptography, and cryptographic hash functions. 
There are many good websites that will go into the "lot more to 
it" without having to have a degree in mathematics to understand 


Peter Verswyvelen wrote:
>> winds up having a write cache, which is mutable in practice.  The
>> interesting thing is that the block's location is the cryptographic
>> hash of its contents, which leads to all sorts of neat properties (as
>> well as requiring immutability).
> That's interesting.  When I developed a version control system for a customer, I also used a cryptographic hash as the database key of file+content in question, but I was afraid I might have clashes (two files with different content generating the same hash)... My intuition told me that the odds of two cryptographic hashes (on meaningful content) colliding was much less than the earth being destroyed by an asteroid... But this is just intuition... What does computer science tell us about this?
> Thank you,
> Peter
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> Haskell-Cafe at

Lanny Ripple <lanny at>
ScmDB / Cisco Systems, Inc.

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