Optical gate for mechanical lock

[zeepia]

Even better would be to inlay a magnetic switch just below the surface. Solid layer of wood with nothing visible. And with strong neodym magnet you can operate a switch...

--- goes to planning something useless with hidden compartments ---

[FFCrash]

An optical gate for a mechanical lock... I had an idea about this.. why not put a clear window (not just a hole, but somethign like an acrylic or glass window) on the plug...shine an LED through one side and put a CCD sensor on the other. On the key, use laser cut holes in a pattern, say 15x15 grid (like a QR code almost). If the light pattern picked up by the CCD doesn't match what's stored in memory, the electronic part of the lock doesn't trigger. Use something like a small ball bearing that protrudes into the keyway as a means to trip a momentary switch that turns the circuit on. The electronic part of the lock would only be used to immobilize the cylinder through something like cam-operated sidebars or something that doesn't protrude into the keyway. The key itself wouldn't even need teeth. The plug itself would still be tied to the heavier-duty mechanical locking mechanism used for the door/deadbolt.

[MrTornado]

I had this idea yesterday as well. I'd just finished typing it all out and then I thought I had better check that no-one else had come up with it and then... Yeah.

There are a few problems with the design that I can imagine off the bat. The first is using vibrations which could cause all the discs to line up due to the light-gates being the light part of the disc. This problem is easily solved by using non-uniform metal.

zeepia - In computering security gained through obscurity isn't secure.

I don't really know how the Abloy Protec works so that may be the exception but with most disk detainer locks they are in theory vunerable to brute forcing although this isn't really a problem when it's far quicker to manipulate them. I am still relativily surprised I haven't seen anyone using a stepper motor and linear actuator to open a disk detainer lock anyway as proof of concept.

The problem with modern disc detainer locks is that there aren't that many combinations. Despite what Abloy say about having a quadrillion combinations or whatever in real terms there are far less. I believe their number comes from factoring in the variety of key shapes but that's not relevent giving current methods of attacking disc detainer locks. The actual number of combinations in a disc detainer lock is highly limited because the gates are large and then fence is large when compared to the discs circumference. This means that there are only 7 (0 to 6) different angles the key needs to be cut to.

For a lock containing 7 code discs that's only 7^7 = 823,543 combinations. This is relativily small considering that it is in no way unheard of that people attack 100^3 = 1,000,000 combination locks using robot dialers. Each individual combination of a disc detainer lock would take less time then a traditional combination lock to enter.

What this really means is that there's a need for a greater resolution on each individual discs If the discs could have 20 unique gate positions then the number of combinations would be 20^7 = 1,280,000,000. Using light instead of a fence would allow that.

Another suggestion I was thinking of was having a chip in the key which when it's inserted into the lock is provided with a OTP by the lock. The key appends a unique identifying number and then hashes the whole lot which is transferred back to the lock which then verifies it.

A further concern with this design would be differential power analysis. This is protected against by locks such as a Kaba Mas but we would have to be very careful.

Forgive the long post.

[GWiens2001]

The ABLOY Protec has 11 discs (19,487,171 key permutations). There are a couple ABLOYs that have 14 discs (105,413,504 key permutations). Of course, that is per key blank.

How many people do you know who carry around even 19 million cut 'try-out' keys?

As for brute force attacks, can't discuss that.

While any lock will have a weakness, picking is not a huge vulnerability with the ABLOY Protec locks.

Good that you are trying to think of improvements. Keep at it!

Gordon