Buckinghamshire CC ANPR cameras

John Wilson tugwilson at gmail.com
Mon Jan 9 16:46:14 GMT 2012

On 9 January 2012 16:34, Roland Perry <lists at internetpolicyagency.com> wrote:
> In article <E1RkGz3-0003TK-Ex at skipnote.org>, Chris Edwards
> <chris-ukcrypto at lists.skipnote.org> writes
>>> They use the 24 bit hash value returned from the camera not the
>>> registration number
>> I guess hashing a registration is pretty easy to reverse.  With access to
>> the DVLA database of all UK registrations, you simply compute the hash for
>> each one.  This is a one off task.  Once you've done it, you know the
>> registration for any given hash.
> Unless the hash changes, with for example the date. You'd still get hashes
> consistent enough to work out how fast the traffic's flowing, but each day
> you get a whole new set of hashes.
> Although if you knew the date the hash was calculated, you could still
> compare the hash you wanted to reverse with the full table, but it's much
> more to compute and store, and could be accused of being security by
> obscurity.

The hash doesn't change over time. There's a FOI response from the
Highways Agency which confirms that.

John Wilson

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