Applet ID's and APDU in Java Card

Question

Hi all,

In my project i want to write biometric data (like fingerprint template) on a smart card. After some good study i chose Java card for my project. But i am new to this platform and know very little about this :(

I have read tutorials from Sun also, but was unable to resolve some confusions:

1.) I just want to read and write biometric data from the card, so is it necessary to design applet for it on java card? Can't i use simple read/write functions of a smart card reader to read/write biometric data on the smart card's memory?

2.) If i create an applet for java card then how i am going to give applet id to it? Applet id is unique to each applet. And, how can i know the applet id for the pre-created applets?

3.) What are Application Protocol Data Unit (APDU's)? And, how are they going to help me in reading/writing data on the card?

I know all these are basic questions but i am really confused. So please help out guys!

Thanks in advance.

Answer 1

Hi Guptamukul,

APDUs are the "commands" you send to the smart card.

Javacards (and applets installed on javacards) support specific APDUs depending on what applets are installed (and specific APDUs for installing applets.) The javacard documentation is the best place to start learning about this.

Some smart cards come with applets pre-installed that have space reserved for biometric data; for example, "PIV" cards (and associated applet).

If your card doesn't have an applet pre-installed for storing biometric data you will need to write and install one.

Hope this helps.