An attacker analyzes the data on two or more magnetic strip cards and is
						able to generate new cards containing valid sequences that allow
						unauthorized access and/or impersonation of individuals. Often, magnetic
						strip encoding methods follow a common format for a given system laid out in
						up to three tracks. A single card may allow access to a corporate office
						complex shared by multiple companies. By analyzing how the data is stored on
						a card, it is also possible to create valid cards via brute-force attacks.
						For example, a single card can grant access to a building, a floor, and a
						suite number. Reading and analyzing data on multiple cards, then performing
						a difference analysis between data encoded on three different cards, can
						reveal clues as to how to generate valid cards that grant access to
						restricted areas of a building or suites/rooms within that building. Data
						stored on magstripe cards is often unencrypted, therefore comparing which
						data changes when two or more cards are analyzed can yield results that aid
						in determining the structure of the card data. A trivial example would be a
						common system data format on a data track which binary encodes the suite
						number of a building that a card will open. By creating multiple cards with
						differing binary encoded segments it becomes possible to enter unauthorized
						areas or pass through checkpoints giving the electronic ID of other
						persons.