Re: Master Key crack
From: Richard Herring (junk_at_[127.0.0.1)
Date: 07/29/03
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Date: Tue, 29 Jul 2003 16:45:25 +0100
In message <3f2677e9$1_2@news.vic.com>, John E. Hadstate
<nospam@null.nil> writes
>
>"Stuart Green" <greens80@hotmail.com> wrote in message
>news:1761049f.0307290239.28dd7f11@posting.google.com...
>> I remeber reading an article about a guy who utilised a master key
>> hack, known to locksmiths, to identify pin placements on a key and
>> grind them down progressively to build a masterkey for a lock.
[...]
>In a simple system producing one Master and one Owner key for each lock,
>each pin position in the lock has two short pins inserted. The length of
>the first pins in each pin position establish the cut heights for the Owner
>keys. The sum of the lengths of the first and second pins in each position
>establish the cut heights for the Master key. The pins come in standard
>lengths, and there are constraints on the maximum height differences between
>adjacent pins. Typical locks come with 4, 5, or 6 pin positions.
>
>There are a finite number of combinations of pins that make up each Master
>series. Thus, one might enumerate all the possible pin placements for owner
>keys for each Master series. Then, given a few owner keys known to be part
>of one Master series, one might search the entire tree of pin combinations
>until one established which Master series included all the given owner keys.
>This would establish the cut lengths for the Master key for that series.
>
>I suspect that for any decent system, you would need a lot more than 4 owner
>keys to establish which Master series they belong to (although there are
>some Master series for 4-pin tumblers that produce a very small number of
>usable owner keys).
>
I think the "master key hack" mentioned by the OP is the one where one
sequentially varies the height of a single pin on one known Owner key to
determine the Master height at that pin. In principle, given one Owner
key and access to the keyhole, that will yield the complete Master
heights using as many blanks as there are pin positions, plus a lot of
filing.
-- Richard Herring
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