Matt Blaze developed a very cool attack against master-key lock systems: <a href="http:&#x2F;&#x2F;www.crypto.com&#x2F;papers&#x2F;mk.pdf" rel="nofollow">http:&#x2F;&#x2F;www.crypto.com&#x2F;papers&#x2F;mk.pdf</a><p>It requires access to one (non-master) key as well as a lock which is open-able by that key.  It also requires being able to generate a modest number of new keys with a key cutter (however significantly fewer than brute forcing the entire space).<p>IIRC, the attack boils down to:
- Start with the known non-master key
- Hold all but one of the teeth constant, and try different values of that one tooth until you get a different working key.  This other value must be the master key&#x27;s value.
- Repeat until you have the master value for each tooth.<p>If TSA locks work the same way as the locks described in this paper, a single lock&#x2F;key seems sufficient to generate the master key.