package org.bouncycastle.crypto.engines;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.OutputLengthException;
import org.bouncycastle.crypto.StreamCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
/**
* HC-128 is a software-efficient stream cipher created by Hongjun Wu. It
* generates keystream from a 128-bit secret key and a 128-bit initialization
* vector.
* <p>
* http://www.ecrypt.eu.org/stream/p3ciphers/hc/hc128_p3.pdf
* </p><p>
* It is a third phase candidate in the eStream contest, and is patent-free.
* No attacks are known as of today (April 2007). See
*
* http://www.ecrypt.eu.org/stream/hcp3.html
* </p>
*/
public class HC128Engine
implements StreamCipher
{
private int[] p = new int[512];
private int[] q = new int[512];
private int cnt = 0;
private static int f1(int x)
{
return rotateRight(x, 7) ^ rotateRight(x, 18)
^ (x >>> 3);
}
private static int f2(int x)
{
return rotateRight(x, 17) ^ rotateRight(x, 19)
^ (x >>> 10);
}
private int g1(int x, int y, int z)
{
return (rotateRight(x, 10) ^ rotateRight(z, 23))
+ rotateRight(y, 8);
}
private int g2(int x, int y, int z)
{
return (rotateLeft(x, 10) ^ rotateLeft(z, 23)) + rotateLeft(y, 8);
}
private static int rotateLeft(
int x,
int bits)
{
return (x << bits) | (x >>> -bits);
}
private static int rotateRight(
int x,
int bits)
{
return (x >>> bits) | (x << -bits);
}
private int h1(int x)
{
return q[x & 0xFF] + q[((x >> 16) & 0xFF) + 256];
}
private int h2(int x)
{
return p[x & 0xFF] + p[((x >> 16) & 0xFF) + 256];
}
private static int mod1024(int x)
{
return x & 0x3FF;
}
private static int mod512(int x)
{
return x & 0x1FF;
}
private static int dim(int x, int y)
{
return mod512(x - y);
}
private int step()
{
int j = mod512(cnt);
int ret;
if (cnt < 512)
{
p[j] += g1(p[dim(j, 3)], p[dim(j, 10)], p[dim(j, 511)]);
ret = h1(p[dim(j, 12)]) ^ p[j];
}
else
{
q[j] += g2(q[dim(j, 3)], q[dim(j, 10)], q[dim(j, 511)]);
ret = h2(q[dim(j, 12)]) ^ q[j];
}
cnt = mod1024(cnt + 1);
return ret;
}
private byte[] key, iv;
private boolean initialised;
private void init()
{
if (key.length != 16)
{
throw new java.lang.IllegalArgumentException(
"The key must be 128 bits long");
}
cnt = 0;
int[] w = new int[1280];
for (int i = 0; i < 16; i++)
{
w[i >> 2] |= (key[i] & 0xff) << (8 * (i & 0x3));
}
System.arraycopy(w, 0, w, 4, 4);
for (int i = 0; i < iv.length && i < 16; i++)
{
w[(i >> 2) + 8] |= (iv[i] & 0xff) << (8 * (i & 0x3));
}
System.arraycopy(w, 8, w, 12, 4);
for (int i = 16; i < 1280; i++)
{
w[i] = f2(w[i - 2]) + w[i - 7] + f1(w[i - 15]) + w[i - 16] + i;
}
System.arraycopy(w, 256, p, 0, 512);
System.arraycopy(w, 768, q, 0, 512);
for (int i = 0; i < 512; i++)
{
p[i] = step();
}
for (int i = 0; i < 512; i++)
{
q[i] = step();
}
cnt = 0;
}
public String getAlgorithmName()
{
return "HC-128";
}
/**
* Initialise a HC-128 cipher.
*
* @param forEncryption whether or not we are for encryption. Irrelevant, as
* encryption and decryption are the same.
* @param params the parameters required to set up the cipher.
* @throws IllegalArgumentException if the params argument is
* inappropriate (ie. the key is not 128 bit long).
*/
public void init(boolean forEncryption, CipherParameters params)
throws IllegalArgumentException
{
CipherParameters keyParam = params;
if (params instanceof ParametersWithIV)
{
iv = ((ParametersWithIV)params).getIV();
keyParam = ((ParametersWithIV)params).getParameters();
}
else
{
iv = new byte[0];
}
if (keyParam instanceof KeyParameter)
{
key = ((KeyParameter)keyParam).getKey();
init();
}
else
{
throw new IllegalArgumentException(
"Invalid parameter passed to HC128 init - "
+ params.getClass().getName());
}
initialised = true;
}
private byte[] buf = new byte[4];
private int idx = 0;
private byte getByte()
{
if (idx == 0)
{
int step = step();
buf[0] = (byte)(step & 0xFF);
step >>= 8;
buf[1] = (byte)(step & 0xFF);
step >>= 8;
buf[2] = (byte)(step & 0xFF);
step >>= 8;
buf[3] = (byte)(step & 0xFF);
}
byte ret = buf[idx];
idx = idx + 1 & 0x3;
return ret;
}
public void processBytes(byte[] in, int inOff, int len, byte[] out,
int outOff) throws DataLengthException
{
if (!initialised)
{
throw new IllegalStateException(getAlgorithmName()
+ " not initialised");
}
if ((inOff + len) > in.length)
{
throw new DataLengthException("input buffer too short");
}
if ((outOff + len) > out.length)
{
throw new OutputLengthException("output buffer too short");
}
for (int i = 0; i < len; i++)
{
out[outOff + i] = (byte)(in[inOff + i] ^ getByte());
}
}
public void reset()
{
idx = 0;
init();
}
public byte returnByte(byte in)
{
return (byte)(in ^ getByte());
}
}