org.bouncycastle.crypto.modes.CTSBlockCipher Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation
Show all versions of bcprov-ext-debug-jdk18on Show documentation
The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.
The newest version!
package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.DefaultBufferedBlockCipher;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.StreamBlockCipher;
/**
* A Cipher Text Stealing (CTS) mode cipher. CTS allows block ciphers to
* be used to produce cipher text which is the same length as the plain text.
*/
public class CTSBlockCipher
extends DefaultBufferedBlockCipher
{
private int blockSize;
/**
* Create a buffered block cipher that uses Cipher Text Stealing
*
* @param cipher the underlying block cipher this buffering object wraps.
*/
public CTSBlockCipher(
BlockCipher cipher)
{
if (cipher instanceof StreamBlockCipher)
{
throw new IllegalArgumentException("CTSBlockCipher can only accept ECB, or CBC ciphers");
}
this.cipher = cipher;
blockSize = cipher.getBlockSize();
buf = new byte[blockSize * 2];
bufOff = 0;
}
/**
* return the size of the output buffer required for an update
* an input of len bytes.
*
* @param len the length of the input.
* @return the space required to accommodate a call to update
* with len bytes of input.
*/
public int getUpdateOutputSize(
int len)
{
int total = len + bufOff;
int leftOver = total % buf.length;
if (leftOver == 0)
{
return total - buf.length;
}
return total - leftOver;
}
/**
* return the size of the output buffer required for an update plus a
* doFinal with an input of len bytes.
*
* @param len the length of the input.
* @return the space required to accommodate a call to update and doFinal
* with len bytes of input.
*/
public int getOutputSize(
int len)
{
return len + bufOff;
}
/**
* process a single byte, producing an output block if necessary.
*
* @param in the input byte.
* @param out the space for any output that might be produced.
* @param outOff the offset from which the output will be copied.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there isn't enough space in out.
* @exception IllegalStateException if the cipher isn't initialised.
*/
public int processByte(
byte in,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
int resultLen = 0;
if (bufOff == buf.length)
{
resultLen = cipher.processBlock(buf, 0, out, outOff);
System.arraycopy(buf, blockSize, buf, 0, blockSize);
bufOff = blockSize;
}
buf[bufOff++] = in;
return resultLen;
}
/**
* process an array of bytes, producing output if necessary.
*
* @param in the input byte array.
* @param inOff the offset at which the input data starts.
* @param len the number of bytes to be copied out of the input array.
* @param out the space for any output that might be produced.
* @param outOff the offset from which the output will be copied.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there isn't enough space in out.
* @exception IllegalStateException if the cipher isn't initialised.
*/
public int processBytes(
byte[] in,
int inOff,
int len,
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException
{
if (len < 0)
{
throw new IllegalArgumentException("Can't have a negative input length!");
}
int blockSize = getBlockSize();
int length = getUpdateOutputSize(len);
if (length > 0)
{
if ((outOff + length) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
}
int resultLen = 0;
int gapLen = buf.length - bufOff;
if (len > gapLen)
{
System.arraycopy(in, inOff, buf, bufOff, gapLen);
resultLen += cipher.processBlock(buf, 0, out, outOff);
System.arraycopy(buf, blockSize, buf, 0, blockSize);
bufOff = blockSize;
len -= gapLen;
inOff += gapLen;
while (len > blockSize)
{
System.arraycopy(in, inOff, buf, bufOff, blockSize);
resultLen += cipher.processBlock(buf, 0, out, outOff + resultLen);
System.arraycopy(buf, blockSize, buf, 0, blockSize);
len -= blockSize;
inOff += blockSize;
}
}
System.arraycopy(in, inOff, buf, bufOff, len);
bufOff += len;
return resultLen;
}
/**
* Process the last block in the buffer.
*
* @param out the array the block currently being held is copied into.
* @param outOff the offset at which the copying starts.
* @return the number of output bytes copied to out.
* @exception DataLengthException if there is insufficient space in out for
* the output.
* @exception IllegalStateException if the underlying cipher is not
* initialised.
* @exception InvalidCipherTextException if cipher text decrypts wrongly (in
* case the exception will never get thrown).
*/
public int doFinal(
byte[] out,
int outOff)
throws DataLengthException, IllegalStateException, InvalidCipherTextException
{
if (bufOff + outOff > out.length)
{
throw new OutputLengthException("output buffer to small in doFinal");
}
int blockSize = cipher.getBlockSize();
int len = bufOff - blockSize;
byte[] block = new byte[blockSize];
if (forEncryption)
{
if (bufOff < blockSize)
{
throw new DataLengthException("need at least one block of input for CTS");
}
cipher.processBlock(buf, 0, block, 0);
if (bufOff > blockSize)
{
for (int i = bufOff; i != buf.length; i++)
{
buf[i] = block[i - blockSize];
}
for (int i = blockSize; i != bufOff; i++)
{
buf[i] ^= block[i - blockSize];
}
if (cipher instanceof CBCModeCipher)
{
BlockCipher c = ((CBCModeCipher)cipher).getUnderlyingCipher();
c.processBlock(buf, blockSize, out, outOff);
}
else
{
cipher.processBlock(buf, blockSize, out, outOff);
}
System.arraycopy(block, 0, out, outOff + blockSize, len);
}
else
{
System.arraycopy(block, 0, out, outOff, blockSize);
}
}
else
{
if (bufOff < blockSize)
{
throw new DataLengthException("need at least one block of input for CTS");
}
byte[] lastBlock = new byte[blockSize];
if (bufOff > blockSize)
{
if (cipher instanceof CBCModeCipher)
{
BlockCipher c = ((CBCModeCipher)cipher).getUnderlyingCipher();
c.processBlock(buf, 0, block, 0);
}
else
{
cipher.processBlock(buf, 0, block, 0);
}
for (int i = blockSize; i != bufOff; i++)
{
lastBlock[i - blockSize] = (byte)(block[i - blockSize] ^ buf[i]);
}
System.arraycopy(buf, blockSize, block, 0, len);
cipher.processBlock(block, 0, out, outOff);
System.arraycopy(lastBlock, 0, out, outOff + blockSize, len);
}
else
{
cipher.processBlock(buf, 0, block, 0);
System.arraycopy(block, 0, out, outOff, blockSize);
}
}
int offset = bufOff;
reset();
return offset;
}
}