Paper 2002/160

Cryptology and Physical Security: Rights Amplification in Master-Keyed Mechanical Locks

Matt Blaze

Abstract

This paper examines mechanical lock security from the perspective of computer science and cryptology. We focus on new and practical attacks for amplifying rights in mechanical pin tumbler locks. Given access to a single master-keyed lock and its associated key, a procedure is given that allows discovery and creation of a working master key for the system. No special skill or equipment, beyond a small number of blank keys and a metal file, is required, and the attacker need engage in no suspicious behavior at the lock's location. Countermeasures are also described that may provide limited protection under certain circumstances. We conclude with directions for research in this area and the suggestion that mechanical locks are worthy objects for study and scrutiny.

Note: Also available at http://www.crypto.com/papers/mk.pdf . Revised final version (6 February 2003)