563.11.1 Java Card Programming

8/3/2019 563.11.1 Java Card Programming

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563.11.1 Java CardProgramming: Overview

Presented by: Raman Sharykin

PISCES Group: Soumyadeb Mitra, Sruthi Bandhakavi, RagibHasan, Raman Sharikyn

University of IllinoisSpring 2006


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Overview

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 ofrestricted resources on card Game of Battleship: Using terminals

memory


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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


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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


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Java Card/Terminal System

APDU = Application Protocol Data Unit

An introduction to Java Card Technology
http://developers.sun.com/techtopics/mobility/javacard/articles/javacard1/http://developers.sun.com/techtopics/mobility/javacard/articles/javacard1/


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Java for Java Cards Features

Small primitive datatypes: boolean, byte,

short. One dimensionalarrays.

Object orientedfeatures: inheritance,virtual methods,dynamic objectcreation, overloading,scope.

Large primitive datatypes: long, double,

float. Characters, strings. Multidimensional

arrays. Dynamic class loading. Garbage collection. Threads. Object Cloning.

Supported Not Supported


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Developing a Java Card Applet

1. Write the Java source2. Compile your source3. Convert the class files into a Converted

Applet (CAP) file (binary representationof classes and interfaces)

4. Verify that the CAP is valid (structure,valid bytecode subset, inter-packagedependencies)

5. Install the CAP file


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Message-Passing Model



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APDU Structure

CLA, INS define the command P1, P2 parameters

Lc data field lentgh Le maximum response length SW1, SW2 response status



10/2010

Applet Structure

import javacard.framework.*...public class MyApplet extends Applet {

// Definitions of APDU-related instruction codes

...MyApplet() {...} // Constructor // Life-cycle methodsinstall() {...}select() {...}deselect() {...}process() {...}

// Private methods ...}


11/2011

Important Methods: Install

install()called when a new applet is being installedpublic 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.


12/2012

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


13/2013

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 valuedefined


14/2014

A Challenge in Java Card Programming

Java Cards have very restricted resources Limited Memory Limited Computing Power

Can we use terminals resources toovercome the restriction provided that theterminal is potentially untrusted?

At Penn we used terminals memory toovercome the first restriction


15/2015

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


16/2016

How to Prevent Cheating?

Before starting the game players assign randomnumbers to each cell, compute the hash of theresulting pair and exchange the tables of hashes

When a player shoots, the opponent providesnot only the contain of the requested cell, butalso the random number assigned to it and thehash

This way the other player can compute the hashof the delivered data and check if it coincideswith the value stored in the beginning.


17/2017

Terminal Services Card

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

We used terminals memory to store thetables of random numbers and hashes To request a services from the terminal we

have two types of respond APDUs The result A request from the card to perform an

operation (store or retrieve data)


18/2018

Terminals Structure

Java Card

Service Layer

Application

Terminal

request

request servicerequest1

servicerepond1 servicerequest2

servicerepond2 respond

respond


19/2019

Data Flow and the Structure of an Applet

Terminal Java Card

Request

Service Request 1

Respond

process(apdu) {.....

switch (message){....

case Request:.....send ServiceRequest1;

break;.....

case ServiceResponde1:.....send ServiceRequest2;

break;.....

case ServiceResponde2:.....send Respond;

}

Service Respond 1

Service Request 2

Service Respond 2


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Future Work

The implementation stores its data on terminalwithout making sure that the server does notalternate the stored data (also it can just look atit!)

The structure of the code on card is complicatedwhen 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

563.11.1 Java Card Programming

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