JCWDE : Exception from install() method

Question

I am working on JavaCard and I developed an applet with JCDE on Eclipse:

import javacard.framework.APDU;
import javacard.framework.Applet;
import javacard.framework.ISO7816;
import javacard.framework.ISOException;
import javacard.framework.Util;
import javacardx.framework.math.BigNumber;
import javacard.security.CryptoException;
import javacard.security.MessageDigest;

public class SignatureGPS extends Applet {
    public static final byte CLA = (byte) 0xB0;
    public static final byte INS = (byte) 0x00;

    private BigNumber s;
    private BigNumber x;
    private MessageDigest h;

    private SignatureGPS() {
        s = new BigNumber((short) 100);
        x = new BigNumber((short) 100);
        try {
            h = MessageDigest.getInstance(MessageDigest.ALG_SHA_256, false);
        } catch (CryptoException e) {
            if (e.getReason() == CryptoException.NO_SUCH_ALGORITHM){
            }
        }
    }


    public static void install(byte bArray[], short bOffset, byte bLength) throws ISOException {
        new SignatureGPS().register();
    }


    public void process(APDU apdu) throws ISOException {
        byte[] buffer = apdu.getBuffer();

        if (this.selectingApplet()) return;

        if (buffer[ISO7816.OFFSET_CLA] != CLA)
            ISOException.throwIt(ISO7816.SW_CLA_NOT_SUPPORTED);

        ...
 }

}

But When I launch JCWDE and APDUTOOL, I have the following errors :

Java Card 2.2.2 APDU Tool, Version 1.3
Copyright 2005 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.
Opening connection to localhost on port 9025.
Connected.
powerup;
// Select the installer applet
0x00 0xA4 0x04 0x00 0x09 0xa0 0x00 0x00 0x00 0x62 0x03 0x01 0x08 0x01 0x7F;
// create SignatureGPS applet
0x80 0xB8 0x00 0x00 0xd 0xb 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x00 0x01 0x00 0x7F;Received ATR = 0x3b 0xf0 0x11 0x00 0xff 0x00 
CLA: 00, INS: a4, P1: 04, P2: 00, Lc: 09, a0, 00, 00, 00, 62, 03, 01, 08, 01, Le: 00, SW1: 90, SW2: 00
// select SignatureGPS applet
0x00 0xA4 0x04 0x00 0xb 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x00 0x01 0x7F;CLA: 80, INS: b8, P1: 00, P2: 00, Lc: 0d, 0b, 01, 02, 03, 04, 05, 06, 07, 08, 09, 00, 01, 00, Le: 00, SW1: 64, SW2: 44

And in Eclipse, JCWDE says

 Exception from the invoked install() method:public static void metispackage.SignatureGPS.install(byte[],short,byte) throws javacard.framework.ISOException

Does anybody know what is going wrong with my install method ? I searched on google but I found nothing to solve my problem :( SW1 = 64 SW2 = 44 indicates that the applet creation failed but I have no idea why...

Answer 1

As you already found out on your own, new BigNumber((short)100); raises an ArithmeticException. You can catch that exception with a try-catch block:

try {
    s = new BigNumber((short)100);
} catch (ArithmeticException e) {
    // TODO: handle exception
}

But that will neither solve the source of the problem nor allow you to use the BigNumber objects as they will never be created.

The constructor of BigNumber raises an ArithmeticException because 100 bytes capacity exceeds the supported maximum capacity of the JCWDE implementation. The API documentation states that implementations of BigNumber only need to support at least 8 bytes. Therefore, you may want to test smaller capacity values in order to find out what the maximum capacity of the JCWDE implementation is.

Answer 2

So, I finally solved my problem... The thing is that s = new BigNumber((short)100) throws an Exception, so I had to modify my code this way :

try {
  s = new BigNumber((short)100);
  x = new BigNumber((short)100);
} catch(ArithmeticException e){

}

And now I can test my applet without problems with JCWDE.