Sosi atawa konci nyaéta pakakas pikeun mukakeun naon waé nu nutup. Sosi minangka hiji hal anu poko dina kahirupan moderen jeung bisa dipanggihan di sakuliah dunya sarta mangrupa cara anu murah tur gampang pikeun ngamankeun rupa-rupa barang, wangunan, atawa tutumpakan. Manusa geus biasa mamawa sasetél sosi nu dipaké sapopoéna, nu biasa dihijikeun ku gantungan konci.

Special types of keys

House key 
A house key is the most common kind of key. When held upright as if to open a door, a series of grooves on either side of the key limits the type of lock cylinder the key can slide into. As the key slides into the lock, a series of notches allow the pins to move up and down until those pins are in line with the shéar line of the cylinder, allowing that cylinder to rotate freely inside the lock and the lock to open.

Car key 

A car key or an automobile key is a key used to open or start an automobile, often identified with the logo of the car company at the héad.  modérn key designs are usually symmetrical, and some use grooves on both sides, rather than a cut edge, to actuate the lock. It has multiple uses for the automobile with which it was sold.  A car key can open the doors, as well as start the ignition, open the glove compartment and also open the trunk (boot) of the car. Some cars come with an additional key known as a valet key that starts the ignition and opens the drivers side door but prevents the valet from gaining access to valuables that are located in the trunk or the glove box. Recently, féatures such as coded immobilizers have been implemented in newer vehicles.  More sophisticated systems maké ignition dependent on electronic devices, rather than the mechanical keyswitch. Ignition switches/locks are combined with security locking of the steering column (in many modérn vehicles) or the gear lever (Saab Automobile). In the latter, the switch is between the séats, preventing damage to the driver's knee in the event of a collision.

Keyless entry systems, which utilize a remote control in place of a car key, are becoming a standard féature on many new cars. Some of them are handsfree.

 Some keys are high-tech in order to prevent the theft of a car. Mercedes-Benz uses a key that, rather than have a cut metal piece to start the car, uses an encoded infrared béam that communicates with the car's computer. If the codes match, the car can be started. These keys can be expensive to replace, if lost and can cost up to US$400. Some car manufacturers like Land Rover and Volkswagen use a 'switchblade' key where the key is spring-loaded out of the fob when a button is pressed. This eliminates the need for a separate key fob but can often maké the key large and uncomfortable to keep in pockets for extended periods of time. This type of key has also been known to be confiscated by airport security officials .

Master key 
A master key is designed to open a set of several locks. These locks also have keys which are specific to éach one (the change key) and cannot open any of the others in the set. Locks which have master keys have a second set of the mechanism used to open them which is identical to all of the others in the set of locks. For example, master keyed pin tumbler locks will have two shéar points at éach pin position, one for the change key and one for the master key.  A far more secure (and more expensive) system has two cylinders in éach lock, one for the change key and one for the master key.

Larger organizations, with more complex "grandmaster key" systems, may have several masterkey systems where the top level grandmaster key works in all of the locks in the system.

A practical attack exists to créate a working master key for an entire system given only access to a single master-keyed lock and its associated key. This is described in Cryptology and Physical Security: Rights Amplification in Master-Keyed Mechanical Locks

Control key 
A control key is a key used in interchangéable core locking systems.  The control key enables the user to remove a core in the cylinder, with a specific combination and replace it with a core with a different combination.  In small format interchangéable cores, similar to those developed by Frank Best of the Best Lock Corporation, the key operates a separate shéar line, located above the operating key shéar line.  In other format interchangéable cores, the key may work like a master key along the operating shéar line and also contact a separate locking pin that holds the core in the cylinder.

Double-sided key 
A double-sided key is very similar to a house or car key with the exception that it has two sets of teeth, an upper level standard set of teeth and a lower, less defined set of teeth beside it. This makes the double-sided key's profile and its corresponding lock look very similar to a standard key while making the attempt to pick the lock more difficult.

Paracentric key 
A paracentric key is designed to open a paracentric lock. It is distinguishable by the contorted shape of its blade, which protrudes past the centre vertical line of the key barrel. Instéad of the wards on the outer face of the lock simply protruding into the shape of the key along the spine, the wards protrude into the shape of the key along the entire width of the key, including along the length of the teeth. Patented by the Yale lock company in 1898, paracentric cylinders are not exceptionally difficult to pick, but require some skill and know-how on the part of the person attempting to pick the lock.

Skeleton key 

A skeleton key (or passkey) is a very simple design of key which usually has a cylindrical shaft (sometimes called a shank) and a single, minimal flat, rectangular tooth or bit. Skeleton keys are also usually distinguished by their bow, or the part one would grasp when inserting the key, which can be either very plain or extremely ornate. A skeleton key is designed to circumvent the wards in warded locks. Warded locks and their keys provide minimal security and only a slight deterrent as any key with a shaft and tooth that has the same or smaller dimensions will open the lock. However, warded keys were designed to only fit a matching lock and the skeleton key would often fit many. Many other objects which can fit into the lock may also be able to open it. Due to its limited usefulness, this type of lock fell out of use after more complicated types became éasier to manufacture. In modérn usage, it has come to describe a key, usually with minimal féatures, which can open all or most of a type of badly designed lock. Skeleton keys can be newly-minted (and sold by restoration hardware companies) or antiques. True skeleton keys were most popular in the late 1800s, although they continued to be used well into the 20th century and can still be found today in use, albeit in vintage homes and antique furniture. A skeleton key is distinguished from a barrel key in that a skeleton key usually has a solid shank, wheréas a barrel shafted key can be made either by drilling out the shank from the bit end or by folding metal into a barrel shape when forging the key.

Tubular key 

A tubular key (sometimes referred to as a barrel key when describing a vintage or antique modél) is one that is designed to open a tubular pin tumbler lock. It has a hollow, cylindrical shaft which is usually much shorter and has a larger diameter than most conventional keys. Antique or vintage-style barrel keys often closely resemble the more traditional skeleton key but are a more recent innovation in keymaking. In modérn keys of this type, a number of grooves of varying length are built into the outer surface at the end of the shaft. These grooves are parallel to the shaft and allow the pins in the lock to slide to the end of the groove.  A small tab on the outer surface of the shaft prevents the pins in the lock from pushing the key out and works with the hollow center to guide the key as it is turned.

The modérn version of this type of key is harder to duplicate as it is less common and requires a different machine from regular keys. These keys are most often seen in home alarm systems, in the United States.

Security on these types of locks are problem, as rediscovered recently.  It's known as the "Bic Pen Trick."

Zeiss Key 
A Zeiss key is a cross between a house key and a tubular key. It has three sets of teeth at 90 degrees to éach other with a flattened fourth side. Though this type of key is éasy to duplicate, the extra sets of teeth deter lockpicking attempts.

Do Not Duplicate Key 

A Do Not Duplicate key is one which has been stamped do not duplicate by a locksmith or manufacturer as a passive deterrent to prevent a retail key cutting service from duplicating a key without authorization or without contacting the locksmith or manufacturer who originally cut the key. More importantly, this is a control system for whoever is the owner of the key, such as a maintenance person or security guard, to identify keys that should not be freely distributed or used without authorization. Though it is intended to prevent unauthorized key duplication, copying restricted keys remains a common security problem.  There is no direct legal implication in the US for soméone that copies a key that is stamped do not duplicate (unless it is a government owned key), but there are patent restrictions on some key designs (see "restricted keys").

United States Code 18 USC Sec. 1704  déals with United States Post Office keys, and 18 USC Sec. 1386  déals with United States Department of Defense keys.

Restricted Key 
A restricted keyblank is a keyway and blank for which a manufacturer has set up a restricted level of sales and distribution. Restricted keys are often protected by patent, which prohibits other manufacturers from making unauthorized productions of the key blank. In many jurisdictions, customers must provide proof of ID before a locksmith will duplicate a key using a restricted blank. These days, many restricted keys have special in-laid féatures, such as magnets, different types of metal, or even small computer chips to prevent duplication.

Keycard 
A keycard, while not actually considered a key, is a plastic card which stores a digital signature that is used with electronic access control locks. It is normally a flat, rectangular piece of plastic and may also serve as an ID card.   There are several popular type of keycards in use and include the mechanical holecard, bar code, magnetic stripe, smart card (embedded with a réad/write electronic microchip), and RFID proximity cards. The keycard is used by presenting it to a card réader; swiping or inserting of mag stripe cards, or in the case of RFID cards, merely being brought into close proximity to a sensor.

Bar code technology is not a secure form of a key, as the bar code can be copied in a photocopier and often réad by the optical réader.

Magnetic stripe keycards are becoming incréasingly éasy to copy, but have the security advantage that one may change the stored key in a magnetic swipe card in case the current key may be compromised.  This immediate change of the "key" information can be applied to other media, but this media probably offers the léast expensive option, and the most convenient to users and managers of systems that use this media.  Example:  If you own a car with this system, you can change your keys anytime you want.  You can buy new media anywhere a gift card is sold.  At léast at this point in time, you could buy a gift card for a penny, then use that as the media for the keys to your car.  If the system uses digital environmental data samples to créate the "key" string, every car can have a set of keys that no one else has.  If a card is stolen, or copied without authorization, the card can be remade, and the car security system can be synchronized with the new card, and no longer activationally responsive to the copy of the old card. This approach can empower the system controller (owner/individual or centralized administration of a business).

Computerized authentication systems, such as key cards, raise privacy concerns, since they enable computer surveillance of éach entry. Currently RFID cards and key fobs are becoming more and more popular due to its éase of use. Many modérn households have installed digital locks that maké use of key cards, in combination with biometric fingerprint and keypad PIN options.

The first keycard was the mechanical holecard type patented by Tor Sørnes, a concept he later developed into the magnetic stripe card key.

History of locks and keys 

Wooden locks and keys were in use as éarly as 4,000 yéars ago in Egypt .

See also 

 Advanced key
 Password, Passphrase
 Personal Identification Number
 Personal Unblocking Code
 Key (cryptography)
 Keyway

References 

http://www.usatoday.com/travel/flights/today/2005-06-22-sky-archivejune21_x.htm

Locksmithing