Barcodes

Data encoding using Barcodes is essentially "free", since the information is encoded on to the card during the printing process. One dimensional (1D) Barcodes are usually printed along the long axis of the card, and are read using swipe readers which use either visible or infrared sensors.

Since the narrowest Barcode "bar" should ideally be at least four pixels wide, practical data capacity is limited to about 20 characters or so.

There are various 1D Barcode systems in use, with Code "3 of 9" being the simplest and probably the most reliable, and Code "I 2 of 5" being the most space efficient.

It is relatively easy to integrate a 1D Barcode encoding scheme into a software application because Barcode formats are available as True-Type fonts, and variable data can be incorporated into the card design during the card issue process.

Barcode Printing

Barcodes should always be printed using the K panel (Black Resin) because this is opaque to both visible and infrared sensors.

As a security measure it is possible to print the black resin Barcode on top of a dark YMC color panel in such a way that it cannot be photocopied, but it can still be read with an infrared swipe reader.

The "height" of a Barcode contains no information, but the higher each bar is made, the easier it may be to read when presented to a reader. About 0.4 inch (1 cm) centered on the swipe reader sensor, should normally be adequate.

Because of the read-only nature of Barcodes and the limitations on data length, 1D Barcodes are usually used to store a single unique character string used as a pass code in access control or other holder identification systems.

Problems to consider include possible security breaches due to the ease of copying the code, and the potential for physical damage to the Barcode after repeated swipes.

Two dimensional (2D) Barcodes appear as a matrix of variable sized square dots and are usually read with a raster-scanning beam sensor housed in a hand held "gun" or in a fixed (supermarket style) reader. Swiping is not required.

The major advantage of a 2D Barcode is its data encoding capacity, with up to 500 bytes per square inch being feasible. Some of this data will normally be used for error correction encoding which also makes the 2D Barcode remarkably tolerant of holes, cuts, and dirt marks.

With around 500 bytes of data available, a 2D Barcode can be used to store biometric data such as a fingerprint, or even a compressed version of the holder's portrait.

Other possibilities include detailed personalized data such as name, address, department, employee number, access authorizations, training status, and expiring date. Since swiping is not required, and 2D Barcodes are very tolerant of artefacts, physical wear should not be a problem, but a potential downside is the higher cost of scanners.