1. The first way is to use " javacard.security.Checksum" class.
Code: Select all
package CRC_Test;
import javacard.framework.*;
import javacard.security.Checksum;
import javacard.security.CryptoException;
public class CRC_Test extends Applet
{
public static void install(byte[] bArray, short bOffset, byte bLength)
{
new CRC_Test().register(bArray, (short) (bOffset + 1), bArray[bOffset]);
}
public void process(APDU apdu)
{
Checksum cs = Checksum.getInstance(Checksum.ALG_ISO3309_CRC32, false);
if (selectingApplet())
{
return;
}
byte[] buf = apdu.getBuffer();
switch (buf[ISO7816.OFFSET_INS])
{
case (byte)0x00:
short lc = apdu.setIncomingAndReceive();
byte[] tmp = JCSystem.makeTransientByteArray((short) 4, JCSystem.CLEAR_ON_DESELECT);
tmp[0] = (byte) 0xFF;
tmp[1] = (byte) 0xFF;
tmp[2] = (byte) 0xFF;
tmp[3] = (byte) 0xFF;
cs.init(tmp, (short) 0, (short) 4);
short ret = cs.doFinal(buf, (short) ISO7816.OFFSET_CDATA, lc, buf, (short) 2);
Util.setShort(buf, (short) 0, ret);
apdu.setOutgoingAndSend((short) 0, (short) 6);
break;
default:
ISOException.throwIt(ISO7816.SW_INS_NOT_SUPPORTED);
}
}
}
Using this method, when I send "11 22 33 44 55", it returns "38 A0 5A 29".
2. The second is to use CRC32 class developed by jcardsim.
Code: Select all
/*
* Copyright 2011 Licel LLC.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.licel.jcardsim.crypto;
import javacard.framework.JCSystem;
import javacard.framework.Util;
import javacard.security.Checksum;
import javacard.security.CryptoException;
/*
* Implementation <code>Checksum</code>
* ISO/IEC 3309 compliant 32 bit CRC algorithm.
* on BouncyCastle CryptoAPI
* @see Checksum
*/
public class CRC32 extends Checksum {
final static byte LENGTH = 4;
private byte crc32[];
private final byte polynom[] = {
4, -63, 29, -73
};
public CRC32() {
crc32 = JCSystem.makeTransientByteArray(LENGTH, JCSystem.CLEAR_ON_DESELECT);
}
public byte getAlgorithm() {
return ALG_ISO3309_CRC32;
}
public void init(byte bArray[], short bOff, short bLen)
throws CryptoException {
if (bLen != LENGTH) {
CryptoException.throwIt(CryptoException.ILLEGAL_VALUE);
}
Util.arrayCopyNonAtomic(bArray, bOff, crc32, (short) 0, bLen);
}
public short doFinal(byte inBuff[], short inOffset, short inLength, byte outBuff[], short outOffset) {
update(inBuff, inOffset, inLength);
for (short i = 0; i < 4; i++) {
crc32[i] ^= 0xff;
}
Util.arrayCopy(crc32, (short) 0, outBuff, outOffset, (short) 4);
Util.arrayFillNonAtomic(crc32, (short) 0, LENGTH, (byte) 0);
return LENGTH;
}
public void update(byte inBuff[], short inOffset, short inLength) {
crc32(inBuff, inOffset, inLength);
}
private void crc32(byte inBuf[], short inOff, short inLen) {
short fcs_h = Util.getShort(crc32, (short) 0);
short fcs_l = Util.getShort(crc32, (short) 2);
short poly_h = Util.getShort(polynom, (short) 0);
short poly_l = Util.getShort(polynom, (short) 2);
byte carry = 0;
for (short i = inOff; i < (short) (inOff + inLen); i++) {
short d_h = (short) (inBuf[i] << 8);
for (short k = 0; k < 8; k++) {
if (((fcs_h ^ d_h) & 0x8000) != 0) {
carry = 0;
short lfcs_h = shift(fcs_h);
if ((fcs_l & 0x8000) != 0) {
carry = 1;
}
short lfcs_l = shift(fcs_l);
if (carry == 1) {
lfcs_h++;
}
fcs_h = (short) (lfcs_h ^ poly_h);
fcs_l = (short) (lfcs_l ^ poly_l);
} else {
carry = 0;
short lfcs_h = shift(fcs_h);
if ((fcs_l & 0x8000) != 0) {
carry = 1;
}
short lfcs_l = shift(fcs_l);
if (carry == 1) {
lfcs_h++;
}
fcs_h = lfcs_h;
fcs_l = lfcs_l;
}
d_h <<= 1;
}
}
Util.setShort(crc32, (short) 2, fcs_l);
Util.setShort(crc32, (short) 0, fcs_h);
}
short shift(short s) {
return s <<= 1;
}
}
When I send "11 22 33 44 55", it returns "6B 05 63 5A".
This result is different with the result of using "javacard.security.Checksum". I m comfused.
Am I making any mistake ?
Which result is the right one?