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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 1.8 and up.
package org.bouncycastle.crypto.modes;
import java.io.ByteArrayOutputStream;
import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.InvalidCipherTextException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.params.AEADParameters;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.Arrays;
/**
* Implementation of DSTU7624 CCM mode
*/
public class KCCMBlockCipher
implements AEADBlockCipher
{
private static final int BYTES_IN_INT = 4;
private static final int BITS_IN_BYTE = 8;
private static final int MAX_MAC_BIT_LENGTH = 512;
private static final int MIN_MAC_BIT_LENGTH = 64;
private BlockCipher engine;
private int macSize;
private boolean forEncryption;
private byte[] initialAssociatedText;
private byte[] mac;
private byte[] macBlock;
private byte[] nonce;
private byte[] G1;
private byte[] buffer;
private byte[] s;
private byte[] counter;
private ExposedByteArrayOutputStream associatedText = new ExposedByteArrayOutputStream();
private ExposedByteArrayOutputStream data = new ExposedByteArrayOutputStream();
private int Nb_ = 4;
private void setNb(int Nb)
{
if (Nb == 4 || Nb == 6 || Nb == 8)
{
Nb_ = Nb;
}
else
{
throw new IllegalArgumentException("Nb = 4 is recommended by DSTU7624 but can be changed to only 6 or 8 in this implementation");
}
}
/**
* Base constructor. Nb value is set to 4.
*
* @param engine base cipher to use under CCM.
*/
public KCCMBlockCipher(BlockCipher engine)
{
this(engine, 4);
}
/**
* Constructor allowing Nb configuration.
*
* Nb is a parameter specified in CCM mode of DSTU7624 standard.
* This parameter specifies maximum possible length of input. It should
* be calculated as follows: Nb = 1/8 * (-3 + log[2]Nmax) + 1,
* where Nmax - length of input message in bits. For practical reasons
* Nmax usually less than 4Gb, e.g. for Nmax = 2^32 - 1, Nb = 4.
*
* @param engine base cipher to use under CCM.
* @param nB Nb value to use.
*/
public KCCMBlockCipher(BlockCipher engine, int nB)
{
this.engine = engine;
this.macSize = engine.getBlockSize();
this.nonce = new byte[engine.getBlockSize()];
this.initialAssociatedText = new byte[engine.getBlockSize()];
this.mac = new byte[engine.getBlockSize()];
this.macBlock = new byte[engine.getBlockSize()];
this.G1 = new byte[engine.getBlockSize()];
this.buffer = new byte[engine.getBlockSize()];
this.s = new byte[engine.getBlockSize()];
this.counter = new byte[engine.getBlockSize()];
setNb(nB);
}
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
CipherParameters cipherParameters;
if (params instanceof AEADParameters)
{
AEADParameters parameters = (AEADParameters)params;
if (parameters.getMacSize() > MAX_MAC_BIT_LENGTH || parameters.getMacSize() < MIN_MAC_BIT_LENGTH || parameters.getMacSize() % 8 != 0)
{
throw new IllegalArgumentException("Invalid mac size specified");
}
nonce = parameters.getNonce();
macSize = parameters.getMacSize() / BITS_IN_BYTE;
initialAssociatedText = parameters.getAssociatedText();
cipherParameters = parameters.getKey();
}
else if (params instanceof ParametersWithIV)
{
nonce = ((ParametersWithIV)params).getIV();
macSize = engine.getBlockSize(); // use default blockSize for MAC if it is not specified
initialAssociatedText = null;
cipherParameters = ((ParametersWithIV)params).getParameters();
}
else
{
throw new IllegalArgumentException("Invalid parameters specified");
}
this.mac = new byte[macSize];
this.forEncryption = forEncryption;
engine.init(true, cipherParameters);
counter[0] = 0x01; // defined in standard
if (initialAssociatedText != null)
{
processAADBytes(initialAssociatedText, 0, initialAssociatedText.length);
}
}
public String getAlgorithmName()
{
return engine.getAlgorithmName() + "/KCCM";
}
public BlockCipher getUnderlyingCipher()
{
return engine;
}
public void processAADByte(byte in)
{
associatedText.write(in);
}
public void processAADBytes(byte[] in, int inOff, int len)
{
associatedText.write(in, inOff, len);
}
private void processAAD(byte[] assocText, int assocOff, int assocLen, int dataLen)
{
if (assocLen - assocOff < engine.getBlockSize())
{
throw new IllegalArgumentException("authText buffer too short");
}
if (assocLen % engine.getBlockSize() != 0)
{
throw new IllegalArgumentException("padding not supported");
}
System.arraycopy(nonce, 0, G1, 0, nonce.length - Nb_ - 1);
intToBytes(dataLen, buffer, 0); // for G1
System.arraycopy(buffer, 0, G1, nonce.length - Nb_ - 1, BYTES_IN_INT);
G1[G1.length - 1] = getFlag(true, macSize);
engine.processBlock(G1, 0, macBlock, 0);
intToBytes(assocLen, buffer, 0); // for G2
if (assocLen <= engine.getBlockSize() - Nb_)
{
for (int byteIndex = 0; byteIndex < assocLen; byteIndex++)
{
buffer[byteIndex + Nb_] ^= assocText[assocOff + byteIndex];
}
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
{
macBlock[byteIndex] ^= buffer[byteIndex];
}
engine.processBlock(macBlock, 0, macBlock, 0);
return;
}
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
{
macBlock[byteIndex] ^= buffer[byteIndex];
}
engine.processBlock(macBlock, 0, macBlock, 0);
int authLen = assocLen;
while (authLen != 0)
{
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
{
macBlock[byteIndex] ^= assocText[byteIndex + assocOff];
}
engine.processBlock(macBlock, 0, macBlock, 0);
assocOff += engine.getBlockSize();
authLen -= engine.getBlockSize();
}
}
public int processByte(byte in, byte[] out, int outOff)
throws DataLengthException, IllegalStateException
{
data.write(in);
return 0;
}
public int processBytes(byte[] in, int inOff, int inLen, byte[] out, int outOff)
throws DataLengthException, IllegalStateException
{
if (in.length < (inOff + inLen))
{
throw new DataLengthException("input buffer too short");
}
data.write(in, inOff, inLen);
return 0;
}
public int processPacket(byte[] in, int inOff, int len, byte[] out, int outOff)
throws IllegalStateException, InvalidCipherTextException
{
if (in.length - inOff < len)
{
throw new DataLengthException("input buffer too short");
}
if (out.length - outOff < len)
{
throw new OutputLengthException("output buffer too short");
}
if (associatedText.size() > 0)
{
if (forEncryption)
{
processAAD(associatedText.getBuffer(), 0, associatedText.size(), data.size());
}
else
{
processAAD(associatedText.getBuffer(), 0, associatedText.size(), data.size() - macSize);
}
}
if (forEncryption)
{
if ((len % engine.getBlockSize()) != 0)
{
throw new DataLengthException("partial blocks not supported");
}
CalculateMac(in, inOff, len);
engine.processBlock(nonce, 0, s, 0);
int totalLength = len;
while (totalLength > 0)
{
ProcessBlock(in, inOff, len, out, outOff);
totalLength -= engine.getBlockSize();
inOff += engine.getBlockSize();
outOff += engine.getBlockSize();
}
for (int byteIndex = 0; byteIndex < counter.length; byteIndex++)
{
s[byteIndex] += counter[byteIndex];
}
engine.processBlock(s, 0, buffer, 0);
for (int byteIndex = 0; byteIndex < macSize; byteIndex++)
{
out[outOff + byteIndex] = (byte)(buffer[byteIndex] ^ macBlock[byteIndex]);
}
System.arraycopy(macBlock, 0, mac, 0, macSize);
reset();
return len + macSize;
}
else
{
if ((len - macSize) % engine.getBlockSize() != 0)
{
throw new DataLengthException("partial blocks not supported");
}
engine.processBlock(nonce, 0, s, 0);
int blocks = len / engine.getBlockSize();
for (int blockNum = 0; blockNum < blocks; blockNum++)
{
ProcessBlock(in, inOff, len, out, outOff);
inOff += engine.getBlockSize();
outOff += engine.getBlockSize();
}
if (len > inOff)
{
for (int byteIndex = 0; byteIndex < counter.length; byteIndex++)
{
s[byteIndex] += counter[byteIndex];
}
engine.processBlock(s, 0, buffer, 0);
for (int byteIndex = 0; byteIndex < macSize; byteIndex++)
{
out[outOff + byteIndex] = (byte)(buffer[byteIndex] ^ in[inOff + byteIndex]);
}
outOff += macSize;
}
for (int byteIndex = 0; byteIndex < counter.length; byteIndex++)
{
s[byteIndex] += counter[byteIndex];
}
engine.processBlock(s, 0, buffer, 0);
System.arraycopy(out, outOff - macSize, buffer, 0, macSize);
CalculateMac(out, 0, outOff - macSize);
System.arraycopy(macBlock, 0, mac, 0, macSize);
byte[] calculatedMac = new byte[macSize];
System.arraycopy(buffer, 0, calculatedMac, 0, macSize);
if (!Arrays.constantTimeAreEqual(mac, calculatedMac))
{
throw new InvalidCipherTextException("mac check failed");
}
reset();
return len - macSize;
}
}
private void ProcessBlock(byte[] input, int inOff, int len, byte[] output, int outOff)
{
for (int byteIndex = 0; byteIndex < counter.length; byteIndex++)
{
s[byteIndex] += counter[byteIndex];
}
engine.processBlock(s, 0, buffer, 0);
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
{
output[outOff + byteIndex] = (byte)(buffer[byteIndex] ^ input[inOff + byteIndex]);
}
}
private void CalculateMac(byte[] authText, int authOff, int len)
{
int totalLen = len;
while (totalLen > 0)
{
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
{
macBlock[byteIndex] ^= authText[authOff + byteIndex];
}
engine.processBlock(macBlock, 0, macBlock, 0);
totalLen -= engine.getBlockSize();
authOff += engine.getBlockSize();
}
}
public int doFinal(byte[] out, int outOff)
throws IllegalStateException, InvalidCipherTextException
{
int len = processPacket(data.getBuffer(), 0, data.size(), out, outOff);
reset();
return len;
}
public byte[] getMac()
{
return Arrays.clone(mac);
}
public int getUpdateOutputSize(int len)
{
return len;
}
public int getOutputSize(int len)
{
return len + macSize;
}
public void reset()
{
Arrays.fill(G1, (byte)0);
Arrays.fill(buffer, (byte)0);
Arrays.fill(counter, (byte)0);
Arrays.fill(macBlock, (byte)0);
counter[0] = 0x01;
data.reset();
associatedText.reset();
if (initialAssociatedText != null)
{
processAADBytes(initialAssociatedText, 0, initialAssociatedText.length);
}
}
private void intToBytes(
int num,
byte[] outBytes,
int outOff)
{
outBytes[outOff + 3] = (byte)(num >> 24);
outBytes[outOff + 2] = (byte)(num >> 16);
outBytes[outOff + 1] = (byte)(num >> 8);
outBytes[outOff] = (byte)num;
}
private byte getFlag(boolean authTextPresents, int macSize)
{
StringBuffer flagByte = new StringBuffer();
if (authTextPresents)
{
flagByte.append("1");
}
else
{
flagByte.append("0");
}
switch (macSize)
{
case 8:
flagByte.append("010"); // binary 2
break;
case 16:
flagByte.append("011"); // binary 3
break;
case 32:
flagByte.append("100"); // binary 4
break;
case 48:
flagByte.append("101"); // binary 5
break;
case 64:
flagByte.append("110"); // binary 6
break;
}
String binaryNb = Integer.toBinaryString(Nb_ - 1);
while (binaryNb.length() < 4)
{
binaryNb = new StringBuffer(binaryNb).insert(0, "0").toString();
}
flagByte.append(binaryNb);
return (byte)Integer.parseInt(flagByte.toString(), 2);
}
private static class ExposedByteArrayOutputStream
extends ByteArrayOutputStream
{
public ExposedByteArrayOutputStream()
{
}
public byte[] getBuffer()
{
return this.buf;
}
}
}
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