Combination lock

History and Evolution of Combination Locks
– Earliest known combination lock found in a Roman period tomb in Athens
Combination locks documented by Al-Jazari and Muhammad al-Asturlabi in the 12th century
Gerolamo Cardano described a combination lock in the 16th century
– US patents by J.B. Gray and J.E. Treat in the 19th century improved combination padlocks
– Joseph Loch made many improvements in combination lock designs in the late 19th and early 20th centuries

Types of Combination Locks
– Multiple-dial locks use rotating discs with notches and a pin with teeth to secure the lock
– Single-dial locks found on padlocks, lockers, or safes use a dial and parallel discs or cams
– C.L. Gougler Keyless Locks Company manufactured locks with audible clicks for the combination
– Andrew Elliot Rae invented a user-settable combination lock in 1978
– Electronic keypad locks became popular for luggage, lockers, and hotel safes

Other Designs and Features
– Many doors use combination locks with numeric keypads for access
– Electronic keypad locks offer the advantage of granting access to multiple users without physical keys
– Electronic combination locks have vulnerabilities such as determining the lock sequence or recent key usage
– Some combination locks encode the secret in an electronic microcontroller for safe and bank vault doors
– These locks allow multiple valid combinations and often have auditing features to record openings

Internal Mechanisms and Security Features
– Relock triggers are integral parts of combination locks and activate when the lock is tampered with
– Thermal relock triggers activate in the event of a torch attack
– Nearly all safes made after World War II have relock triggers in their combination locks

Notable Facts and Tips for Using Combination Locks
– Combination locks use a sequence of symbols, usually numbers, to open the lock
– Combination locks range from inexpensive three-digit luggage locks to high-security safes
– Combination locks do not use keys like ordinary padlocks
– Combination locks can be opened by aligning notches or by entering the correct permutation
– Electronic combination locks may scramble numbers randomly to prevent attacks
– Tips for using combination locks include choosing a unique combination, regular maintenance, and keeping the combination confidentialSources: