uuid types 3 and 5

[Richard Gaskin]

Martin Baxter wrote:
> I have read that type 3 is deprecated, on the basis that md5 is not
> considered secure these days, although I think that was one thing that
> confused me because uuid is nothing to do with encryption or obfuscation
> as far as I was aware.

The difference is reliability.  The value of a hash is that it produces 
a unique string for a unique input.  But with MD5 (and to a lesser 
degree SHA1 also - we could really use another hash function in LC), 
it's been shown that two different inputs can produce the same output.

With small collections this is unlikely to be a problem, but since the 
purpose of a UUID is to deliver a unique identifier, any algo that can 
produce the same output from two different inputs would be unsuitable.

--
  Richard Gaskin
  Fourth World
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