Lock (security device)

Iron Lock from Sirpur, India Excavation, 12th century

historical Locks from 17th century Russia

A lock is a mechanical or electronic fastening device that is released by a physical object (such as a key, keycard, fingerprint, RFID card, security token etc.), by supplying secret information (such as a keycode or password), or by a combination thereof.

History

Antiquity

Medieval lock in Kathmandu

Ancient Lock from Kerala

The earliest known lock and key device was discovered in the ruins of Nineveh, the capital of ancient Assyria.^[1] Locks such as this were later developed into the Egyptian wooden pin lock, which consisted of a bolt, door fixture, and key. When the key was inserted, pins within the fixture were lifted out of drilled holes within the bolt, allowing it to move. When the key was removed, the pins fell part-way into the bolt, preventing movement.^[2]

Simple three-disc locking mechanism
from a wooden box recovered from
the Swedish ship Vasa, sunk in 1628

The warded lock was also present from antiquity and remains the most recognizable lock and key design in the Western world. The first all-metal locks appeared between the years 870 and 900, and are attributed to the English craftsmen.^[3] It is also said that the key was invented by Theodore of Samos in the 6th century BC.^[4]

Affluent Romans often kept their valuables in secure boxes within their households, and wore the keys as rings on their fingers. The practice had two benefits: It kept the key handy at all times, while signaling that the wearer was wealthy and important enough to have money and jewelry worth securing.^[5]

Modern locks

Chinese lock and key from Yunnan Province, early 20th century

With the onset of the Industrial Revolution in the late 18th century and the concomitant development of precision engineering and component standardisation, locks and keys were manufactured with increasing complexity and sophistication.

The lever tumbler lock, which uses a set of levers to prevent the bolt from moving in the lock, was perfected by Robert Barron in 1778. His double acting lever lock required the lever to be lifted to a certain height by having a slot cut in the lever, so lifting the lever too far was as bad as not lifting the lever far enough. This type of lock is still currently used today.^[6]

Diagram of a Chubb detector lock

The lever tumbler lock was greatly improved by Jeremiah Chubb in 1818. A burglary in Portsmouth Dockyard prompted the British Government to announce a competition to produce a lock that could be opened only with its own key.^[7] Chubb developed the Chubb detector lock, which incorporated an integral security feature that could frustrate unauthorised access attempts and would indicate to the lock's owner if it had been interfered with. Chubb was awarded £100 after a trained lock-picker failed to break the lock after 3 months.^[8]

In 1820, Jeremiah joined his brother Charles in starting their own lock company, Chubb. Chubb made various improvements to his lock: his 1824 improved design didn't require a special regulator key to reset the lock; by 1847 his keys used six levers rather than four; and he later introduced a disc that allowed the key to pass but narrowed the field of view, hiding the levers from anybody attempting to pick the lock.^[9] The Chubb brothers also received a patent for the first burglar-resisting safe and began production in 1835.

The designs of Barron and Chubb were based on the use of movable levers, but Joseph Bramah, a prolific inventor, developed an alternative method in 1784. His lock used a cylindrical key with precise notches along the surface; these moved the metal slides that impeded the turning of the bolt into an exact alignment, allowing the lock to open. The lock was at the limits of the precision manufacturing capabilities of the time and was said by its inventor to be unpickable. In the same year Bramah started the Bramah Locks company at 124 Piccadilly, and displayed the "Challenge Lock" in the window of his shop from 1790, challenging "...the artist who can make an instrument that will pick or open this lock" for the reward of £200. The challenge stood for over 67 years until, at the Great Exhibition of 1851, the American locksmith Alfred Charles Hobbs was able to open the lock and, following some argument about the circumstances under which he had opened it, was awarded the prize. Hobbs' attempt required some 51 hours, spread over 16 days.

The earliest patent for a double-acting pin tumbler lock was granted to American physician Abraham O. Stansbury in England in 1805,^[10] but the modern version, still in use today, was invented by American Linus Yale, Sr. in 1848.^[11] This lock design used pins of varying lengths to prevent the lock from opening without the correct key. In 1861, Linus Yale, Jr. was inspired by the original 1840s pin-tumbler lock designed by his father, thus inventing and patenting a smaller flat key with serrated edges as well as pins of varying lengths within the lock itself, the same design of the pin-tumbler lock which still remains in use today.^[12] The modern Yale lock is essentially a more developed version of the Egyptian lock.

Despite some improvement in key design since, the majority of locks today are still variants of the designs invented by Bramah, Chubb and Yale.

Types of locks

Locks with physical keys

Pin tumbler lock: without a key in the lock, the driver pins (blue) are pushed downwards, preventing the plug (yellow) from rotating

Tubular lock: the key pins (red) and driver pins (blue) are pushed towards the front of the lock, preventing the plug (yellow) from rotating. The tubular key has several half-cylinder indentations which align with the pins

Wafer tumbler lock: without a key in the lock, the wafers (red) are pushed down by springs. The wafers nestle into a groove in the lower part of the outer cylinder (green) preventing the plug (yellow) from rotating

A warded lock uses a set of obstructions, or wards, to prevent the lock from opening unless the correct key is inserted. The key has notches or slots that correspond to the obstructions in the lock, allowing it to rotate freely inside the lock. Warded locks are typically reserved for low-security applications as a well-designed skeleton key can successfully open a wide variety of warded locks.

The pin tumbler lock uses a set of pins to prevent the lock from opening unless the correct key is inserted. The key has a series of grooves on either side of the key's blade that limit the type of lock the key can slide into. As the key slides into the lock, the horizontal grooves on the blade align with the wards in the keyway allowing or denying entry to the cylinder. A series of pointed teeth and notches on the blade, called bittings, then allow pins to move up and down until they are in line with the shear line of the inner and outer cylinder, allowing the cylinder or cam to rotate freely and the lock to open.

A wafer tumbler lock is similar to the pin tumbler lock and works on a similar principle. However, unlike the pin lock (where each pin consists of two or more pieces) each wafer is a single piece. The wafer tumbler lock is often incorrectly referred to as a disc tumbler lock, which uses an entirely different mechanism. The wafer lock is relatively inexpensive to produce and is often used in automobiles and cabinetry.

The disc tumbler lock or Abloy lock is composed of slotted rotating detainer discs. They are considered very secure and almost impossible to pick.

The lever tumbler lock uses a set of levers to prevent the bolt from moving in the lock. In its simplest form, lifting the tumbler above a certain height will allow the bolt to slide past. Lever locks are commonly recessed inside wooden doors or on some older forms of padlocks, including fire brigade padlocks.

Locks with electronic keys

An electronic lock works by means of an electric current and is usually connected to an access control system. In addition to the pin and tumbler used in standard locks, electronic locks connects the bolt or cylinder to a motor within the door using a part called an actuator. Types of electronic locks include the following:

A keycard lock operates with a flat card using the same dimensions as a credit card or US and EU driver's license. In order to open the door, one needs to successfully match the signature within the keycard.

A smart lock is an electromechanics lock that gets instructions to lock and unlock the door from an authorized device using a cryptographic key and wireless protocol. Smart locks have begun to be used more commonly in residential areas, often controlled with smartphones.^[13][14] Smart locks are used in coworking spaces and offices to enable keyless office entry.^[15]

The sidebar lock operates using fins on a radial key that actuate sidebars that align with a cylindrical code bar within the lock. This is a new type of master key technology developed by the Australian Lock Company. The keys and the code bar are cut using a computer numerical control (CNC) machine.

Locksmithing

Locksmith, 1451

A Chinese locksmith in Jakarta (Batavia) around 1870

A Chinese locksmith in Singapore, circa 1900

Locksmithing is a traditional trade, and in most countries requires completion of an apprenticeship. The level of formal education required varies from country to country, from a simple training certificate awarded by an employer, to a full diploma from an engineering college. Locksmiths may be commercial (working out of a storefront), mobile (working out of a vehicle), institutional, or investigational (forensic locksmiths). They may specialize in one aspect of the skill, such as an automotive lock specialist, a master key system specialist or a safe technician. Many also act as security consultants, but not all security consultants have the skills and knowledge of a locksmith.

Historically, locksmiths constructed or repaired an entire lock, including its constituent parts. The rise of cheap mass production has made this less common; the vast majority of locks are repaired through like-for-like replacements, high-security safes and strongboxes being the most common exception. Many locksmiths also work on any existing door hardware, including door closers, hinges, electric strikes, and frame repairs, or service electronic locks by making keys for transponder-equipped vehicles and implementing access control systems.

Although the fitting and replacement of keys remains an important part of locksmithing, modern locksmiths are primarily involved in the installation of high quality lock-sets and the design, implementation, and management of keying and key control systems. A locksmith is frequently required to determine the level of risk to an individual or institution and then recommend and implement appropriate combinations of equipment and policies to create a "security layer" that exceeds the reasonable gain of an intruder.

Full disclosure

Full disclosure requires that full details of a security vulnerability are disclosed to the public, including details of the vulnerability and how to detect and exploit it. The theory behind full disclosure is that releasing vulnerability information immediately results in better security. Fixes are produced faster because vendors and authors are forced to respond in order to protect their system from potential attacks as well as to protect their own image. Security is improved because the window of exposure, the amount of time the vulnerability is open to attack, is reduced. The issue of full disclosure was first raised in a 19th-century controversy over the revelation of lock-system weaknesses to the public. According to A. C. Hobbs:

A commercial, and in some respects a social doubt has been started within the last year or two, whether or not it is right to discuss so openly the security or insecurity of locks. Many well-meaning persons suppose that the discussion respecting the means for baffling the supposed safety of locks offers a premium for dishonesty, by showing others how to be dishonest. This is a fallacy. Rogues are very keen in their profession, and know already much more than we can teach them respecting their several kinds of roguery.

Rogues knew a good deal about lock-picking long before locksmiths discussed it among themselves, as they have lately done. If a lock, let it have been made in whatever country, or by whatever maker, is not so inviolable as it has hitherto been deemed to be, surely it is to the interest of honest persons to know this fact, because the dishonest are tolerably certain to apply the knowledge practically;and the spread of the knowledge is necessary to give fair play to those who might suffer by ignorance.

It cannot be too earnestly urged that an acquaintance with real facts will, in the end, be better for all parties. Some time ago, when the reading public was alarmed at being told how London milk is adulterated, timid persons deprecated the exposure, on the plea that it would give instructions in the art of adulterating milk; a vain fear, milkmen knew all about it before, whether they practiced it or not; and the exposure only taught purchasers the necessity of a little scrutiny and caution, leaving them to obey this necessity or not, as they pleased.

— A. C. Hobbs (Charles Tomlinson, ed.), Locks and Safes: The Construction of Locks. Published by Virtue & Co., London, 1853 (revised 1868).

Famous locksmiths

• William F. Banham, founder of Banham Security, invented the first automatic latch bolt lock in 1926 after a series of burglaries on his wife's dress shop. He opened up his own locksmith shop on Oxford Street, London, and offered £25 to anyone who could pick or break one of his patented locks ^[16][17] Banham Group still offer the patented locks.^[18][19][20]
• Robert Barron patented a double-acting tumbler lock in 1778, the first reasonable improvement in lock security.
• Joseph Bramah patented the Bramah lock in 1784.^[21] It was considered unpickable for 67 years until A.C. Hobbs picked it, taking over 50 hours.^[22]
• Jeremiah Chubb patented his detector lock in 1818. It won him the reward offered by the Government for a lock that could not be opened by any but its own key.
• James Sargent described the first successful key-changeable combination lock in 1857. His lock became popular with safe manufacturers and the United States Treasury Department. In 1873, he patented a time lock mechanism, the prototype for those used in contemporary bank vaults.
• Samuel Segal of the Segal Lock and Hardware Company invented the first jimmy-proof locks in 1916.
• Harry Soref founded the Master Lock Company in 1921 and patented an improved padlock in 1924 with a patent lock casing constructed out of laminated steel.
• Linus Yale, Sr. invented a pin tumbler lock in 1848.
• Linus Yale, Jr. improved upon his father's lock in 1861, using a smaller, flat key with serrated edges that is the basis of modern pin-tumbler locks. Yale developed the modern combination lock in 1862.
• Alfred Charles Hobbs demonstrated the inadequacy of several respected locks of the time in 1851 at The Great Exhibition, and popularized the practice of full disclosure.

See also

• Access control
• Associated Locksmiths of America
• Door security
• Industrial revolution
• Exit control lock
• Master Locksmiths Association
• Physical security
• Rope lock
• Security door chain

Types of locks

• Bicycle lock
• Cam lock
• Chamber lock
• Child safety lock
• Combination lock
• Cylinder lock
• Dead bolt
• Electronic lock
• Electric strike
• Magnetic lock
• Mortise lock
• Lever tumbler lock
• Lock screen
• Chubb detector lock
• Police lock
• Protector lock
• Luggage lock
• Magnetic keyed lock
• Padlock
• Rim lock
• Time lock

References

Further reading

• Phillips, Bill. (2005). The Complete Book of Locks and Locksmithing. McGraw-Hill. ISBN 0-07-144829-2.
• Alth, Max (1972). All About Locks and Locksmithing. Penguin. ISBN 0-8015-0151-2
• Robinson, Robert L. (1973). Complete Course in Professional Locksmithing Nelson-Hall. ISBN 0-911012-15-X

External links

Wikibooks has more on the topic of: Lock (security device)

Wikimedia Commons has media related to Locks (security devices).

• Lockwiki
• "Historical locks" by Raine Borg and ASSA ABLOY
• "Picking Locks", Popular Mechanics