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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 with debug enabled.
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;
import org.bouncycastle.util.Arrays;
/**
* An implementation of the CBC mode for GOST 3412 2015 cipher.
* See GOST R 3413 2015
*/
public class G3413CBCBlockCipher
implements BlockCipher
{
private int m;
private int blockSize;
private byte[] R;
private byte[] R_init;
private BlockCipher cipher;
private boolean initialized = false;
private boolean forEncryption;
/**
* @param cipher base cipher
*/
public G3413CBCBlockCipher(BlockCipher cipher)
{
this.blockSize = cipher.getBlockSize();
this.cipher = cipher;
}
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
this.forEncryption = forEncryption;
if (params instanceof ParametersWithIV)
{
ParametersWithIV ivParam = (ParametersWithIV)params;
byte[] iv = ivParam.getIV();
if (iv.length < blockSize)
{
throw new IllegalArgumentException("Parameter m must blockSize <= m");
}
this.m = iv.length;
initArrays();
R_init = Arrays.clone(iv);
System.arraycopy(R_init, 0, R, 0, R_init.length);
// if null it's an IV changed only.
if (ivParam.getParameters() != null)
{
cipher.init(forEncryption, ivParam.getParameters());
}
}
else
{
setupDefaultParams();
initArrays();
System.arraycopy(R_init, 0, R, 0, R_init.length);
// if it's null, key is to be reused.
if (params != null)
{
cipher.init(forEncryption, params);
}
}
initialized = true;
}
/**
* allocate memory for R and R_init arrays
*/
private void initArrays()
{
R = new byte[m];
R_init = new byte[m];
}
/**
* this method sets default values to m parameter:
* m = blockSize
*/
private void setupDefaultParams()
{
this.m = blockSize;
}
public String getAlgorithmName()
{
return cipher.getAlgorithmName() + "/CBC";
}
public int getBlockSize()
{
return blockSize;
}
public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException
{
return (forEncryption) ? encrypt(in, inOff, out, outOff) : decrypt(in, inOff, out, outOff);
}
private int encrypt(byte[] in, int inOff, byte[] out, int outOff)
{
byte[] msb = GOST3413CipherUtil.MSB(R, blockSize);
byte[] input = GOST3413CipherUtil.copyFromInput(in, blockSize, inOff);
byte[] sum = GOST3413CipherUtil.sum(input, msb);
byte[] c = new byte[sum.length];
cipher.processBlock(sum, 0, c, 0);
System.arraycopy(c, 0, out, outOff, c.length);
if (out.length > (outOff + sum.length))
{
generateR(c);
}
return c.length;
}
private int decrypt(byte[] in, int inOff, byte[] out, int outOff)
{
byte[] msb = GOST3413CipherUtil.MSB(R, blockSize);
byte[] input = GOST3413CipherUtil.copyFromInput(in, blockSize, inOff);
byte[] c = new byte[input.length];
cipher.processBlock(input, 0, c, 0);
byte[] sum = GOST3413CipherUtil.sum(c, msb);
System.arraycopy(sum, 0, out, outOff, sum.length);
if (out.length > (outOff + sum.length))
{
generateR(input);
}
return sum.length;
}
/**
* generate new R value
*
* @param C processed block
*/
private void generateR(byte[] C)
{
byte[] buf = GOST3413CipherUtil.LSB(R, m - blockSize);
System.arraycopy(buf, 0, R, 0, buf.length);
System.arraycopy(C, 0, R, buf.length, m - buf.length);
}
public void reset()
{
if (initialized)
{
System.arraycopy(R_init, 0, R, 0, R_init.length);
cipher.reset();
}
}
}
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