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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 .