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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.

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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;

/**
 * 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 version applies the CTS algorithm from one block up, rather than following the errata update issued in 2004, where CTS mode is applied * from greater than 1 block up and the first block is processed using CBC mode. *

*/ public class OldCTSBlockCipher extends BufferedBlockCipher { private int blockSize; /** * Create a buffered block cipher that uses Cipher Text Stealing * * @param cipher the underlying block cipher this buffering object wraps. */ public OldCTSBlockCipher( BlockCipher cipher) { if ((cipher instanceof OFBBlockCipher) || (cipher instanceof CFBBlockCipher)) { 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 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 DataLengthException("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 DataLengthException("output buffer to small in doFinal"); } int blockSize = cipher.getBlockSize(); int len = bufOff - blockSize; byte[] block = new byte[blockSize]; if (forEncryption) { cipher.processBlock(buf, 0, block, 0); if (bufOff < blockSize) { throw new DataLengthException("need at least one block of input for CTS"); } 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 CBCBlockCipher) { BlockCipher c = ((CBCBlockCipher)cipher).getUnderlyingCipher(); c.processBlock(buf, blockSize, out, outOff); } else { cipher.processBlock(buf, blockSize, out, outOff); } System.arraycopy(block, 0, out, outOff + blockSize, len); } else { byte[] lastBlock = new byte[blockSize]; 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); } int offset = bufOff; reset(); return offset; } }




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