Access Control Cards.
A Card is a Card is a Card?
Sort of... Maybe.
Magnetic and proximity cards are most commonly used today.
Proximity cards are "hands-free." These cards don't have to be inserted into a reader, but will be recognized when they are in the vicinity (a few inches or a few feet) of the reader. While the general acceptance of proximity cards has grown, the most popular type of access control card is magnetic-stripe.
Magnetic cards are first encoded, then inserted into a reader which senses the code. There are three different data tracks that have been approved for use in magnetic cards. Each track has defined encoding formats. As long as the magnetic stripe is located per standardized ISO specifications, the card can be any size and still be used in swipe-through card readers.
The process and materials used to make magnetic cards is relatively simple (which is good and bad). The stripe itself is a coating of iron oxide or other substance that can be magnetized and demagnetized. It's similar to a bar magnet.
Some magnetic stripes require more coercivity than others. (Coercivity is the strength of a magnetic field required to record or change data on the magnetic strip.) Everyday magnets can erase a low-coercivity magnetic stripe; those with high coercivity, as with most in access control cards, are virtually non-erasable.
Information is recorded on the stripe in digital form--numbers and alphabetic characters. Since it's not hard to manufacture the cards, the process includes protection against unauthorized duplicating. Manufacturers offer proprietary encoders that encode some or all of the numbers into a secret form or code. 123456 might become 781420. It would be almost impossible, without knowing the secret code, to transform the recorded information back into the actual "coded number."
So, while a card may be a card may be a card, it becomes unique when it belongs to an individual!
This article was first published in Volume 3, Edition 1 in the Intelligent Security newsletter--a newsletter published for the security professional by PSA Security Network.