Re: [IP] Master Key Copying Revealed (Matt Blaze of ATT Labs)

[Arnold G. Reinhold]

I took a look at the "MIT Guide to Lock Picking" August 1991 revision at
http://www.lysator.liu.se/mit-guide/mit-guide.html

It says:

"9.10 Master Keys
Many applications require keys that open only a single lock and keys that open a group of locks. The keys that open a single lock are called change keys and the keys that open multiple locks are called master keys. To allow both the change key and the master key to open the same lock, a locksmith adds an extra pin called a spacer to some of the pin columns. See Figure 9.8. The effect of the spacer is to create two gaps in the pin column that could be lined up with the sheer line. Usually the change key aligns the top of the spacer with the sheer line, and the master key aligns the bottom of the spacer with the sheer line (the idea is to prevent people from filing down a change key to get a master key). In either case the plug is free to rotate."

The parenthetical comment suggests awareness of the general vulnerability Matt exploited, but I suspect that had the authors known the multiple partial copy trick Matt described, they would have published it.

Arnold Reinhold

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