// Copyright (c) 2003-2014, Jodd Team (jodd.org). All Rights Reserved.
package jodd.joy.crypt;
import jodd.util.buffer.FastByteBuffer;
/**
* Generic block chipher.
*/
public abstract class BlockCipher {
protected static final byte TERMINATOR = -1;
protected final int blockSizeInBytes;
protected BlockCipher(int blockSize) {
this.blockSizeInBytes = blockSize >> 3;
}
/**
* Encrypts single block of plain content. It ensures that there is
* always a block size amount of data.
*/
protected abstract byte[] encryptBlock(byte[] content, int offset);
/**
* Decrypts single block of encrypted content.
*/
protected abstract byte[] decryptBlock(byte[] encryptedContent, int offset);
/**
* Encrypts complete content, block by block.
*/
public byte[] encrypt(byte[] content) {
FastByteBuffer fbb = new FastByteBuffer();
int length = content.length + 1;
int blockCount = length / blockSizeInBytes;
int remaining = length;
int offset = 0;
for (int i = 0; i < blockCount; i++) {
if (remaining == blockSizeInBytes) {
break;
}
byte[] encrypted = encryptBlock(content, offset);
fbb.append(encrypted);
offset += blockSizeInBytes;
remaining -= blockSizeInBytes;
}
if (remaining != 0) {
// process remaining bytes
byte[] block = new byte[blockSizeInBytes];
System.arraycopy(content, offset, block, 0, remaining - 1);
block[remaining - 1] = TERMINATOR;
byte[] encrypted = encryptBlock(block, 0);
fbb.append(encrypted);
}
return fbb.toArray();
}
/**
* Decrypts the whole content, block by block.
*/
public byte[] decrypt(byte[] encryptedContent) {
FastByteBuffer fbb = new FastByteBuffer();
int length = encryptedContent.length;
int blockCount = length / blockSizeInBytes;
int offset = 0;
for (int i = 0; i < blockCount - 1; i++) {
byte[] decrypted = decryptBlock(encryptedContent, offset);
fbb.append(decrypted);
offset += blockSizeInBytes;
}
// process last block
byte[] decrypted = decryptBlock(encryptedContent, offset);
// find terminator
int ndx = blockSizeInBytes - 1;
while (ndx >= 0) {
if (decrypted[ndx] == TERMINATOR) {
break;
}
ndx--;
}
fbb.append(decrypted, 0, ndx);
return fbb.toArray();
}
}