Lampiran 9 : Class Mode Enkripsi CFB (CFBBlockCipher.java)
9. Lampiran 9 : Class Mode Enkripsi CFB (CFBBlockCipher.java)
package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher; import org.bouncycastle.crypto.CipherParameters; import org.bouncycastle.crypto.DataLengthException; import org.bouncycastle.crypto.params.ParametersWithIV;
/** * implements a Cipher-FeedBack (CFB) mode on top of a simple cipher. */
public class CFBBlockCipher implements BlockCipher { private byte[] IV; private byte[] cfbV; private byte[] cfbOutV;
private int blockSize; private BlockCipher cipher = null; private boolean encrypting;
/** * Basic constructor. * * @param cipher the block cipher to be used as the basis of the * feedback mode. * @param bitBlockSize the block size in bits (note: a multiple of 8) */
public CFBBlockCipher( BlockCipher cipher, int bitBlockSize)
{ this.cipher = cipher; this.blockSize = bitBlockSize / 8;
this.IV = new byte[cipher.getBlockSize()]; this.cfbV = new byte[cipher.getBlockSize()]; this.cfbOutV = new byte[cipher.getBlockSize()];
/** * return the underlying block cipher that we are wrapping. * * @return the underlying block cipher that we are wrapping.
*/ public BlockCipher getUnderlyingCipher() {
return cipher; }
/** * Initialise the cipher and, possibly, the initialisation vector (IV). * If an IV isn't passed as part of the parameter, the IV will be all zeros.
* An IV which is too short is handled in FIPS compliant fashion. * * @param encrypting if true the cipher is initialised for * encryption, if false for decryption. * @param params the key and other data required by the cipher. * @exception IllegalArgumentException if the params argument is * inappropriate. */
public void init( boolean encrypting, CipherParameters params) throws IllegalArgumentException
{ this.encrypting = encrypting;
if (params instanceof ParametersWithIV) {
ParametersWithIV ivParam = (ParametersWithIV)params; byte[] iv = ivParam.getIV();
if (iv.length < IV.length) {
// prepend the supplied IV with zeros (per FIPS PUB 81) System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length); for (int i = 0; i < IV.length - iv.length; i++) {
IV[i] = 0; } } else {
System.arraycopy(iv, 0, IV, 0, IV.length); }
reset();
cipher.init(true, ivParam.getParameters());
} else {
reset();
cipher.init(true, params); } }
/** * return the algorithm name and mode. * * @return the name of the underlying algorithm followed by "/CFB" * and the block size in bits. */
public String getAlgorithmName() {
return cipher.getAlgorithmName() + "/CFB" + (blockSize * 8);
/** * return the block size we are operating at. * * @return the block size we are operating at (in bytes). */
public int getBlockSize() {
return blockSize; }
/** * Process one block of input from the array in and write it to * the out array. * * @param in the array containing the input data. * @param inOff offset into the in array the data starts at. * @param out the array the output data will be copied into. * @param outOff the offset into the out array the output will start
at. * @exception DataLengthException if there isn't enough data in in, or * space in out. * @exception IllegalStateException if the cipher isn't initialised. * @return the number of bytes processed and produced. */
public int processBlock(
byte[] in, int inOff, byte[] out, int outOff) throws DataLengthException, IllegalStateException
{ return (encrypting) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff); }
/** * Do the appropriate processing for CFB mode encryption. * * @param in the array containing the data to be encrypted. * @param inOff offset into the in array the data starts at. * @param out the array the encrypted data will be copied into. * @param outOff the offset into the out array the output will start
at. * @exception DataLengthException if there isn't enough data in in, or * space in out. * @exception IllegalStateException if the cipher isn't initialised. * @return the number of bytes processed and produced. */
public int encryptBlock( byte[] in, int inOff, byte[] out, int outOff) throws DataLengthException, IllegalStateException
{ if ((inOff + blockSize) > in.length) {
throw new DataLengthException("input buffer too short"); }
if ((outOff + blockSize) > out.length) {
throw new DataLengthException("output buffer too short"); }
cipher.processBlock(cfbV, 0, cfbOutV, 0);
// // XOR the cfbV with the plaintext producing the ciphertext // for (int i = 0; i < blockSize; i++) {
out[outOff + i] = (byte)(cfbOutV[i] ^ in[inOff + i]);
// // change over the input block. // System.arraycopy(cfbV,
0, cfbV.length - blockSize); System.arraycopy(out, outOff, cfbV, cfbV.length - blockSize, blockSize);
blockSize,
cfbV,
return blockSize; }
/** * Do the appropriate processing for CFB mode decryption. * * @param in the array containing the data to be decrypted. * @param inOff offset into the in array the data starts at. * @param out the array the encrypted data will be copied into. * @param outOff the offset into the out array the output will start
at. * @exception DataLengthException if there isn't enough data in in, or * space in out. * @exception IllegalStateException if the cipher isn't initialised. * @return the number of bytes processed and produced. */
public int decryptBlock( byte[] in, int inOff, byte[] out, int outOff) throws DataLengthException, IllegalStateException
{ if ((inOff + blockSize) > in.length) {
throw new DataLengthException("input buffer too short"); }
if ((outOff + blockSize) > out.length) {
throw new DataLengthException("output buffer too short"); }
cipher.processBlock(cfbV, 0, cfbOutV, 0);
106
// change over the input block. // System.arraycopy(cfbV,
0, cfbV.length - blockSize); System.arraycopy(in, inOff, cfbV, cfbV.length - blockSize, blockSize);
blockSize,
cfbV,
// // XOR the cfbV with the ciphertext producing the plaintext // for (int i = 0; i < blockSize; i++) {
out[outOff + i] = (byte)(cfbOutV[i] ^ in[inOff + i]);
return blockSize; }
/** * reset the chaining vector back to the IV and reset the underlying * cipher. */
public void reset() {
System.arraycopy(IV, 0, cfbV, 0, IV.length);