Buckinghamshire CC ANPR cameras

Ian Batten igb at batten.eu.org
Mon Feb 6 11:11:39 GMT 2012

On 6 Feb 2012, at 10:24, John Wilson wrote:
> I'm not sniffy about contributors to Dr Dobbs. Back in the day it was
> a good deal more useful to the working programmer than the ACM
> Communications.

That's not the point.  The hash function that you cited was designed for table lookup.  There's a lot of such functions, and their properties are fairly well understood.  But the application it's being used for here isn't a table lookup: it's data anonymisation.   It's different.  Before worrying about which journal you're going to look in, you need to know what it is you want to achieve.  And a table-lookup hash function probably doesn't have those properties.  For example, it has no need to make the average hamming distance between two outputs independent of the hamming distance between the inputs, whereas for anonymisation I'd say that was likely to be essential.  It's fine if the output from a table-lookup function sorts into the same order as its inputs (ie, f(x)>f(y) => x>y) but that would be suicidal in anonymisation.


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