Just read CRYPTO-GRAM, February 15, 2003. (A sometimes interesting newsletter.)

Back issues are available at 
<http://www.counterpane.com/crypto-gram.html>.  To subscribe, visit 
<http://www.counterpane.com/crypto-gram.html> or send a blank message 
to crypto-gram-subscribe@chaparraltree.com.
And saw this article about a guy at AT&T Labs who applied an "oracle attack" to master-key-lock systems producing a master-key in minutes.
Is your door safe? :P

Blaze's home page for his research:

The paper itself:

The reaction to the paper:

News articles on the research:

Previous web references to Blaze's technique:

Jewel theft using the master key vulnerability: