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package org.spongycastle.crypto.modes;
import org.spongycastle.crypto.BlockCipher;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.DataLengthException;
import org.spongycastle.crypto.params.KeyParameter;
import org.spongycastle.crypto.params.ParametersWithIV;
import org.spongycastle.crypto.params.ParametersWithRandom;
import org.spongycastle.crypto.params.ParametersWithSBox;
/**
* An implementation of the GOST CFB mode with CryptoPro key meshing as described in RFC 4357.
*/
public class GCFBBlockCipher
implements BlockCipher
{
private static final byte[] C =
{
0x69, 0x00, 0x72, 0x22, 0x64, (byte)0xC9, 0x04, 0x23,
(byte)0x8D, 0x3A, (byte)0xDB, (byte)0x96, 0x46, (byte)0xE9, 0x2A, (byte)0xC4,
0x18, (byte)0xFE, (byte)0xAC, (byte)0x94, 0x00, (byte)0xED, 0x07, 0x12,
(byte)0xC0, (byte)0x86, (byte)0xDC, (byte)0xC2, (byte)0xEF, 0x4C, (byte)0xA9, 0x2B
};
private final CFBBlockCipher cfbEngine;
private KeyParameter key;
private long counter = 0;
private boolean forEncryption;
public GCFBBlockCipher(BlockCipher engine)
{
this.cfbEngine = new CFBBlockCipher(engine, engine.getBlockSize() * 8);
}
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
counter = 0;
cfbEngine.init(forEncryption, params);
this.forEncryption = forEncryption;
if (params instanceof ParametersWithIV)
{
params = ((ParametersWithIV)params).getParameters();
}
if (params instanceof ParametersWithRandom)
{
params = ((ParametersWithRandom)params).getParameters();
}
if (params instanceof ParametersWithSBox)
{
params = ((ParametersWithSBox)params).getParameters();
}
key = (KeyParameter)params;
}
public String getAlgorithmName()
{
return "G" + cfbEngine.getAlgorithmName();
}
public int getBlockSize()
{
return cfbEngine.getBlockSize();
}
public int processBlock(byte[] in, int inOff, byte[] out, int outOff)
throws DataLengthException, IllegalStateException
{
if (counter > 0 && counter % 1024 == 0)
{
BlockCipher base = cfbEngine.getUnderlyingCipher();
base.init(false, key);
byte[] nextKey = new byte[32];
base.processBlock(C, 0, nextKey, 0);
base.processBlock(C, 8, nextKey, 8);
base.processBlock(C, 16, nextKey, 16);
base.processBlock(C, 24, nextKey, 24);
key = new KeyParameter(nextKey);
byte[] iv = new byte[8];
base.init(true, key);
base.processBlock(cfbEngine.getCurrentIV(), 0, iv, 0);
cfbEngine.init(forEncryption, new ParametersWithIV(key, iv));
}
counter += cfbEngine.getBlockSize();
return cfbEngine.processBlock(in, inOff, out, outOff);
}
public void reset()
{
counter = 0;
cfbEngine.reset();
}
}
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