Bill Graydon - Duplicating Restricted Mechanical Keys

Breaking Restricted Key Systems

Bill Graydon presents research demonstrating that restricted mechanical key systems — keys marketed as 'uncopyable' due to patent restrictions on key blanks — can be defeated using accessible technology.

How Restricted Key Systems Work

Restricted key systems (Medeco, Mul-T-Lock, Abloy Protec) use proprietary key blank profiles available only to licensed dealers and require mandatory dealer verification before cutting. The business model relies on blank scarcity rather than cryptographic security.

3D Printing Key Blanks

Using open-source 3D printing files for documented restricted key profiles, Graydon creates functional PLA and resin key blanks that fit restricted cylinders. While early prints lacked the tensile strength for heavy padlocks, modern SLS-printed nylon blanks operate comparably to metal blanks for light-duty cylinders.

Photogrammetric Key Cloning

By briefly photographing a restricted key against a known-measurement reference background, the exact cut depths can be measured photogrammetrically and replicated on a key cutting machine, bypassing the need for a restricted blank entirely.