/*
* 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 16 bit CRC algorithm
* on BouncyCastle CryptoAPI.
* @see Checksum
*/
public class CRC16 extends Checksum {
static final byte LENGTH = 2;
private byte crc16[];
public CRC16() {
crc16 = JCSystem.makeTransientByteArray(LENGTH, JCSystem.CLEAR_ON_DESELECT);
}
public byte getAlgorithm() {
return ALG_ISO3309_CRC16;
}
public void init(byte bArray[], short bOff, short bLen)
throws CryptoException {
if (bLen != LENGTH) {
CryptoException.throwIt(CryptoException.ILLEGAL_VALUE);
}
Util.arrayCopyNonAtomic(bArray, bOff, crc16, (short) 0, bLen);
}
public short doFinal(byte inBuff[], short inOffset, short inLength, byte outBuff[], short outOffset) {
update(inBuff, inOffset, inLength);
short temp = Util.getShort(crc16, (short) 0);
temp = (short) (~temp);
Util.setShort(crc16, (short) 0, temp);
Util.arrayCopy(crc16, (short) 0, outBuff, outOffset, (short) 2);
Util.arrayFillNonAtomic(crc16, (short) 0, (short) LENGTH, (byte) 0);
return LENGTH;
}
public void update(byte inBuff[], short inOffset, short inLength) {
crc16(inBuff, inOffset, inLength);
}
void crc16(byte inBuf[], short inOff, short inLen) {
short fcs = Util.getShort(crc16, (short) 0);
for (short i = inOff; i < (short) (inOff + inLen); i++) {
short d = (short) (inBuf[i] << 8);
for (short k = 0; k < 8; k++) {
if ((short) ((fcs ^ d) & 0x8000) != 0) {
fcs = (short) ((short) (fcs << 1) ^ 0x1021);
} else {
fcs <<= 1;
}
d <<= 1;
}
}
Util.setShort(crc16, (short) 0, fcs);
}
}