A Java Card Primer, Part 1

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Originally published at Internet.com

To begin, I would like to offer some background on smart cards, for which Sun Microsystems introduced its Java Card technology. This advance has made it easier for high-level programmers to start writing code even for smart cards that were restricted to a machine-level specific language. And with this convenience and ease, I am sure there will be more ideas and applications to come to market to really take us into the Twenty-first century.

Overview of Smart Cards

Smart cards are also called chip cards or integrated circuit cards. The integrated circuit is incorporated in the credit-card-size plastic substrate. The integrated circuit performs the logic of manipulating or processing the data.

Basic Card Types

* Memory cards: They are embedded with a memory chip to store small amounts of data. They do not have a processor to provide intelligence. The simple data processing is done by burned programmed logic and circuitry logic, which has obviously restricted functionalities. * Microprocessor cards: They come with a processor. * Contact cards: Card must be inserted in some device to communicate. * Contactless cards: These types of cards don't need a CAD. They communicate using electromagnetic fields.

Smart Card Communication Model

Smart Cards are inserted into a CAD (Card Acceptance Device). The CAD is connected to some computer, where the applications that reside are known as host applications. These communicate with the applet downloaded or masked in cards. The host application sends commands to the applets in the smart cards. These commands are known as Command APDUs (Application Protocol Data Unit). The applet in the smart card responds by sending response APDUs.

Command APDU Structure

Response APDU Structure

Java Card Technology

Java Card technology provides the smallest Java platform for memory-constrained devices such as smart cards.

Basics of the Java Card

A Java Card means a smart card that is enabled to work with Java Card Technology.