 A letter combination lock. A combination lock is a type of lock in which a sequence of numbers or symbols is used to open the lock. The sequence may be entered using a single rotating dial which interacts with several discs or cams, by using a set of several rotating discs with inscribed numerals which directly interact with the locking mechanism, or through an electronic or mechanical keypad. Gerolamo Cardano is generally credited with the invention of the combination lock. Image File history File linksMetadata Size of this preview: 597 × 599 pixelsFull resolution (1443 × 1449 pixel, file size: 196 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Combination lock User:Mysid/otherimages Metadata...
Image File history File linksMetadata Size of this preview: 597 × 599 pixelsFull resolution (1443 × 1449 pixel, file size: 196 KB, MIME type: image/jpeg) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Combination lock User:Mysid/otherimages Metadata...
Padlock A lock is a mechanical fastening device which may be used on a door, vehicle, or container, restricting access to the area or property enclosed. ...
Gerolamo Cardano. ...
What is commonly referred to as a combination lock is really a permutation lock--the proper sequence of numbers is required to open the lock, not just any arbitrary combination of the solution numbers. In this article, the term combination lock is used to represent a permutation lock, consistent with common usage. (True combination locks are inherently inferior to permutation locks.) Permutation is the rearrangement of objects or symbols into distinguishable sequences. ...
In combinatorial mathematics, a combination is an un-ordered collection of unique elements. ...
Exploded view of the rotating discs. The notches on the disc correspond to the numerals in the correct combination. In this case, the combination is 9-2-4.
The discs are mounted on one side of the lock, which may in turn be attached to the end of a chain or cable. The other side of the lock, or the other end of the cable, has a pin with several protruding teeth.
When the toothed pin is inserted and the discs are rotated to an incorrect combination, the inner faces of the discs block the pin from being extracted. Illustration of a simple combination lock created by Wapcaplet in Blender and touched up in GIMP. File links The following pages link to this file: Combination lock Categories: GFDL images | Images created with Blender ...
Illustration of a simple combination lock created by Wapcaplet in Blender and touched up in GIMP. File links The following pages link to this file: Combination lock Categories: GFDL images | Images created with Blender ...
Illustration of a simple combination lock created by Wapcaplet in Blender and touched up in GIMP. File links The following pages link to this file: Combination lock Categories: GFDL images | Images created with Blender ...
Design
Multiple-dial locks One of the simplest types of combination lock, often seen in low-security bicycle locks, uses several rotating discs with notches cut into them. The lock is secured by a pin with several teeth on it which hook into the rotating discs. When the notches in the discs align with the teeth on the pin, the lock can be opened. “Velo†redirects here. ...
This lock is considered to be one of the least secure types of combination lock; many locks of this type can be quickly opened without knowledge of the correct combination. Opening one in this fashion depends on slight irregularities in the machining of the parts. Unless the lock is machined precisely, when the pin is pulled outward, one of the teeth will pull more strongly than the others on its corresponding disc. This disc is then rotated until a slight click is heard, indicating that the tooth has settled into the notch. The procedure is repeated for the remaining discs, resulting in an open lock, and a correct combination, in very little time.
 A single-dial padlock. Image File history File links ComboLock. ...
Single-dial locks Combination locks found on padlocks or safes may use a single dial which interacts with several parallel discs or cams. Customarily, a lock of this type is opened by rotating the dial clockwise to the first numeral, counterclockwise to the second, and so on in an alternating fashion until the last numeral is reached; the cams typically have an indentation or notch, and when the correct combination is entered, the notches align, allowing the latch to fit into them and open the lock. Padlock A modern padlock. ...
A typical home safe. ...
Depending on the quality of the lock, some single-dial combination locks can also be defeated relatively easily. Typical padlocks are manufactured with generous tolerances, allowing two, three or even more digits of 'play' in the correct access sequence. Given a 60-number dial with three cams and three digits of play, the search space is reduced from 60 × 60 × 60 to 20 × 20 × 20, a 96% reduction in potential combinations.
Additionally, if testing the mechanism to open the lock does not modify the state of the lock, multiple combinations can be tried sequentially, drastically reducing the brute force search time. The first two digits are entered normally once, then, starting from the second digit, the dial is rotated sequentially through the digits, testing the lock on each. If it takes three seconds to input the first digit, two seconds for the second digit, and one second for the third digit, then the normal search time for a 60-number dial with three cams would be (3 + 2 + 1) × 60³. The reduced search time would be (3 + 2 + 60) × 60², a reduction of nearly 82% from 360 hours to 65 hours. This strategy can be extended to the second digit as well, slightly reducing the search time further. The EFFs US$250,000 DES cracking machine contained over 1,800 custom chips and could brute force a DES key in a matter of days — the photograph shows a DES Cracker circuit board fitted with several Deep Crack chips. ...
When these two strategies are combined on a lock with the properties given above, the brute force search time is reduced by greater than 99%; a brute force search that would have taken 360 hours is reduced to an achievable 2.78 hours. This is still significantly better security than multiple-dial locks and many keyed locks, but unacceptable for high security applications.
Inexpensive padlocks are often also susceptible to direct mechanical attacks, such as the use of a padlock shim which can release the shackle without entering a combination. Early combination padlocks made by Master lock could be cracked by pulling on the shackle of the lock and turning the dial until it stopped; each numeral in the combination could be revealed in this manner. More recent models of Master padlock with a 40-position dial have a mechanical weakness that can give away the last numeral in the combination, and the first two numerals have a mathematical relationship with the last number. This weakness reduces the number of possible combinations from 64,000 to a mere 100, which can be tried in a relatively short time. Master Lock is a manufacturer of padlocks and combination locks. ...
Other designs Many doors use combination locks which require the user to enter a numeric sequence on a keypad to facilitate entry. These special locks usually require the additional use of electronic circuitry. The chief advantage of this system is that if used for the door of a large office, each employee can be told the code number without having to supply a key to each person. However, if the code number is learnt by someone outside the desired group or is not changed regularly, it could allow easy access to a potential intruder (the same could be said for all combination and keyed locks, and many other security measures, however). Look up Keyboard in Wiktionary, the free dictionary A keyboard can refer to a: Alphanumeric keyboard, any keyboard that has both letter and numbers on it Typewriter keyboard Computer keyboard IBM PC keyboard Musical keyboard, a keyboard on a musical instrument Keyboard instrument, such as the piano Keyboard synthesizer, a...
Electronic combination locks, while generally safe from the attacks on their mechanical counterparts, suffer from their own set of flaws. It is much easier to determine the lock sequence by viewing several successful accesses, since the arrangement of numbers is fixed. Similarly, the numbers in the combination (but not the actual permutation) can be determined by which keys show signs of recent use. An electronic lock is a locking device which uses some form of electronics to authenticate those accessing it, sometimes using two-factor authentication. ...
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