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563.11.1 Java Card Programming: Overview . Presented by: Raman Sharykin PISCES Group: Soumyadeb Mitra, Sruthi Bandhakavi, Ragib Hasan, Raman Sharikyn University of Illinois Spring 2006. Overview. Java Cards Java Card/Terminal System Features of Java for Java Cards compared to Java

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563 11 1 java card programming overview

563.11.1 Java Card Programming: Overview

Presented by: Raman Sharykin

PISCES Group: Soumyadeb Mitra, Sruthi Bandhakavi, Ragib Hasan, Raman Sharikyn

University of Illinois

Spring 2006


  • Java Cards

  • Java Card/Terminal System

  • Features of Java for Java Cards compared to Java

  • Java Card Applets: Developing Cycle

  • Structure of Applets and Messages

  • On approach to overcome the issue of restricted resources on card

  • Game of Battleship: Using terminal’s memory

Java card features
Java Card Features

  • Receives clock and power from terminal

  • Three types of memory:

    • Random Access Memory (RAM)

    • Read-Only Memory (ROM)

    • Erasable Read-Only Memory (EEPROM)

  • Restricted Resources

    • Slow and simple microprocessor (8-bit)

    • RAM ~1Kb

    • ROM ~64Kb

    • EEPROM ~16-64Kb

  • Restricted Version of Java

The use of java cards
The use of Java Cards

  • SIM cards in cell phones

  • Identity cards (government, health-care)

  • Financial cards supporting online and offline transactions

  • Smart tickets for mass transit

Java card terminal system
Java Card/Terminal System

APDU = Application Protocol Data Unit

An introduction to Java Card Technology

Java for java cards features

Small primitive data types: boolean, byte, short.

One dimensional arrays.

Object oriented features: inheritance, virtual methods, dynamic object creation, overloading, scope.

Large primitive data types: long, double, float.

Characters, strings.

Multidimensional arrays.

Dynamic class loading.

Garbage collection.


Object Cloning.

Java for Java Cards Features


Not Supported

Developing a java card applet
Developing a Java Card Applet

  • Write the Java source

  • Compile your source

  • Convert the class files into a Converted Applet (CAP) file (binary representation of classes and interfaces)

  • Verify that the CAP is valid (structure, valid bytecode subset, inter-package dependencies)

  • Install the CAP file

Message passing model
Message-Passing Model

An introduction to Java Card Technology

Apdu structure
APDU Structure

  • CLA, INS define the command

  • P1, P2 – parameters

  • Lc – data field lentgh

  • Le – maximum response length

  • SW1, SW2 – response status

An introduction to Java Card Technology

Applet structure
Applet Structure

  • import javacard.framework.*

  • ...

  • public class MyApplet extends Applet {

    • // Definitions of APDU-related instruction codes

    • ...

    • MyApplet() {...} // Constructor

    • // Life-cycle methods

    • install() {...}

    • select() {...}

    • deselect() {...}

    • process() {...}

    • // Private methods ...

  • }

Important methods install
Important Methods: Install

  • install()

    called when a new applet is being installed

    public static void install

    ( byte[] bArray, short bOffset, byte bLength) {

    new myApplet(null);


    • Must call register() to let JCRE know that a new applet has been installed.

Important methods select deselect
Important Methods: Select/Deselect

  • select()

    • when we want to use an applet

    • is called when SELECT APDU is received

  • deselect()

    • is called when another SELECT APDU is received

Important methods use
Important Methods: Use

  • process()

    • when an APDU is received and applet is selected its method process is called to process the APDU

    • the selected applet parses the APDU and perform whatever it needs to perform

    • normally the body of process() method is a big switch with code for each INS value defined

A challenge in java card programming
A Challenge in Java Card Programming

  • Java Cards have very restricted resources

    • Limited Memory

    • Limited Computing Power

  • Can we use terminal’s resources to overcome the restriction provided that the terminal is potentially untrusted?

  • At Penn we used terminal’s memory to overcome the first restriction

Game of battleship
Game of Battleship

  • Playing Field is n by n

  • Ships are vertical or horizontal and of a fixed length

  • Players shoot in turns

  • The winner is the player who has eliminated the ships of the opponent first

How to prevent cheating
How to Prevent Cheating?

  • Before starting the game players assign random numbers to each cell, compute the hash of the resulting pair and exchange the tables of hashes

  • When a player shoots, the opponent provides not only the contain of the requested cell, but also the random number assigned to it and the hash

  • This way the other player can compute the hash of the delivered data and check if it coincides with the value stored in the beginning.

Terminal services card
Terminal Services Card

  • If we want to play the game on 10 by 10 field we need 10*10*16*2 = 3200 bytes when only ~600 is available

  • We used terminal’s memory to store the tables of random numbers and hashes

  • To request a services from the terminal we have two types of respond APDU’s

    • The result

    • A request from the card to perform an operation (store or retrieve data)

Terminal s structure
Terminal’s Structure





Service Layer











Java Card

Data flow and the structure of an applet
Data Flow and the Structure of an Applet


Java Card

process(apdu) {


switch (message){


case Request:


send ServiceRequest1;



case ServiceResponde1:


send ServiceRequest2;



case ServiceResponde2:


send Respond;



Service Request 1

Service Respond 1

Service Request 2

Service Respond 2


Future work
Future Work

  • The implementation stores its data on terminal without making sure that the server does not alternate the stored data (also it can just look at it!)

  • The structure of the code on card is complicated when we need Service Requests

    • inside a function call

    • inside a loop

  • It would be interesting to know if we can use the computational power of the terminal as well