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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 JDK 1.5 to JDK 1.8. Note: this package includes the NTRU encryption algorithms.
/**
* 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.
*/
package org.bouncycastle.crypto.modes;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.BufferedBlockCipher;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.OutputLengthException;
/**
* 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.
*
* This class implements the NIST version as documented in "Addendum to NIST SP 800-38A, Recommendation for Block Cipher Modes of Operation: Three Variants of Ciphertext Stealing for CBC Mode"
*
*/
public class NISTCTSBlockCipher
extends BufferedBlockCipher
{
public static final int CS1 = 1;
public static final int CS2 = 2;
public static final int CS3 = 3;
private final int type;
private final int blockSize;
/**
* Create a buffered block cipher that uses NIST Cipher Text Stealing
*
* @param type type of CTS mode (CS1, CS2, or CS3)
* @param cipher the underlying block cipher used to create the CBC block cipher this cipher uses..
*/
public NISTCTSBlockCipher(
int type,
BlockCipher cipher)
{
this.type = type;
this.cipher = new CBCBlockCipher(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 org.bouncycastle.crypto.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 org.bouncycastle.crypto.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 org.bouncycastle.crypto.DataLengthException if there is insufficient space in out for
* the output.
* @exception IllegalStateException if the underlying cipher is not
* initialised.
* @exception org.bouncycastle.crypto.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 NISTCTS");
}
if (bufOff > blockSize)
{
byte[] lastBlock = new byte[blockSize];
if (this.type == CS2 || this.type == CS3)
{
cipher.processBlock(buf, 0, block, 0);
System.arraycopy(buf, blockSize, lastBlock, 0, len);
cipher.processBlock(lastBlock, 0, lastBlock, 0);
if (this.type == CS2 && len == blockSize)
{
System.arraycopy(block, 0, out, outOff, blockSize);
System.arraycopy(lastBlock, 0, out, outOff + blockSize, len);
}
else
{
System.arraycopy(lastBlock, 0, out, outOff, blockSize);
System.arraycopy(block, 0, out, outOff + blockSize, len);
}
}
else
{
System.arraycopy(buf, 0, block, 0, blockSize);
cipher.processBlock(block, 0, block, 0);
System.arraycopy(block, 0, out, outOff, len);
System.arraycopy(buf, bufOff - len, lastBlock, 0, len);
cipher.processBlock(lastBlock, 0, lastBlock, 0);
System.arraycopy(lastBlock, 0, out, outOff + len, blockSize);
}
}
else
{
cipher.processBlock(buf, 0, block, 0);
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 (this.type == CS3 || (this.type == CS2 && ((buf.length - bufOff) % blockSize) != 0))
{
if (cipher instanceof CBCBlockCipher)
{
BlockCipher c = ((CBCBlockCipher)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
{
BlockCipher c = ((CBCBlockCipher)cipher).getUnderlyingCipher();
c.processBlock(buf, bufOff - blockSize, lastBlock, 0);
System.arraycopy(buf, 0, block, 0, blockSize);
if (len != blockSize)
{
System.arraycopy(lastBlock, len, block, len, blockSize - len);
}
cipher.processBlock(block, 0, block, 0);
System.arraycopy(block, 0, out, outOff, blockSize);
for (int i = 0; i != len; i++)
{
lastBlock[i] ^= buf[i];
}
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;
}
}