using System;
using Org.BouncyCastle.Crypto.Parameters;
namespace Org.BouncyCastle.Crypto.Engines{
/**
* Implementation of Bob Jenkin's ISAAC (Indirection Shift Accumulate Add and Count).
* see: http://www.burtleburtle.net/bob/rand/isaacafa.html
*/
public class IsaacEngine
: IStreamCipher
{
// Constants
private static readonly int sizeL = 8,
stateArraySize = sizeL<<5; // 256
// Cipher's internal state
private uint[] engineState = null, // mm
results = null; // randrsl
private uint a = 0, b = 0, c = 0;
// Engine state
private int index = 0;
private byte[] keyStream = new byte[stateArraySize<<2], // results expanded into bytes
workingKey = null;
private bool initialised = false;
/**
* initialise an ISAAC cipher.
*
* @param forEncryption whether or not we are for encryption.
* @param params the parameters required to set up the cipher.
* @exception ArgumentException if the params argument is
* inappropriate.
*/
public void Init(
bool forEncryption,
ICipherParameters parameters)
{
if (!(parameters is KeyParameter))
throw new ArgumentException(
"invalid parameter passed to ISAAC Init - " + parameters.GetType().Name,
"parameters");
/*
* ISAAC encryption and decryption is completely
* symmetrical, so the 'forEncryption' is
* irrelevant.
*/
KeyParameter p = (KeyParameter) parameters;
setKey(p.GetKey());
}
public byte ReturnByte(
byte input)
{
if (index == 0)
{
isaac();
keyStream = intToByteLittle(results);
}
byte output = (byte)(keyStream[index]^input);
index = (index + 1) & 1023;
return output;
}
public void ProcessBytes(
byte[] input,
int inOff,
int len,
byte[] output,
int outOff)
{
if (!initialised)
throw new InvalidOperationException(AlgorithmName + " not initialised");
if ((inOff + len) > input.Length)
throw new DataLengthException("input buffer too short");
if ((outOff + len) > output.Length)
throw new DataLengthException("output buffer too short");
for (int i = 0; i < len; i++)
{
if (index == 0)
{
isaac();
keyStream = intToByteLittle(results);
}
output[i+outOff] = (byte)(keyStream[index]^input[i+inOff]);
index = (index + 1) & 1023;
}
}
public string AlgorithmName
{
get { return "ISAAC"; }
}
public void Reset()
{
setKey(workingKey);
}
// Private implementation
private void setKey(
byte[] keyBytes)
{
workingKey = keyBytes;
if (engineState == null)
{
engineState = new uint[stateArraySize];
}
if (results == null)
{
results = new uint[stateArraySize];
}
int i, j, k;
// Reset state
for (i = 0; i < stateArraySize; i++)
{
engineState[i] = results[i] = 0;
}
a = b = c = 0;
// Reset index counter for output
index = 0;
// Convert the key bytes to ints and put them into results[] for initialization
byte[] t = new byte[keyBytes.Length + (keyBytes.Length & 3)];
Array.Copy(keyBytes, 0, t, 0, keyBytes.Length);
for (i = 0; i < t.Length; i+=4)
{
results[i>>2] = byteToIntLittle(t, i);
}
// It has begun?
uint[] abcdefgh = new uint[sizeL];
for (i = 0; i < sizeL; i++)
{
abcdefgh[i] = 0x9e3779b9; // Phi (golden ratio)
}
for (i = 0; i < 4; i++)
{
mix(abcdefgh);
}
for (i = 0; i < 2; i++)
{
for (j = 0; j < stateArraySize; j+=sizeL)
{
for (k = 0; k < sizeL; k++)
{
abcdefgh[k] += (i<1) ? results[j+k] : engineState[j+k];
}
mix(abcdefgh);
for (k = 0; k < sizeL; k++)
{
engineState[j+k] = abcdefgh[k];
}
}
}
isaac();
initialised = true;
}
private void isaac()
{
uint x, y;
b += ++c;
for (int i = 0; i < stateArraySize; i++)
{
x = engineState[i];
switch (i & 3)
{
case 0: a ^= (a << 13); break;
case 1: a ^= (a >> 6); break;
case 2: a ^= (a << 2); break;
case 3: a ^= (a >> 16); break;
}
a += engineState[(i+128) & 0xFF];
engineState[i] = y = engineState[(int)((uint)x >> 2) & 0xFF] + a + b;
results[i] = b = engineState[(int)((uint)y >> 10) & 0xFF] + x;
}
}
private void mix(uint[] x)
{
// x[0]^=x[1]<< 11; x[3]+=x[0]; x[1]+=x[2];
// x[1]^=x[2]>>> 2; x[4]+=x[1]; x[2]+=x[3];
// x[2]^=x[3]<< 8; x[5]+=x[2]; x[3]+=x[4];
// x[3]^=x[4]>>>16; x[6]+=x[3]; x[4]+=x[5];
// x[4]^=x[5]<< 10; x[7]+=x[4]; x[5]+=x[6];
// x[5]^=x[6]>>> 4; x[0]+=x[5]; x[6]+=x[7];
// x[6]^=x[7]<< 8; x[1]+=x[6]; x[7]+=x[0];
// x[7]^=x[0]>>> 9; x[2]+=x[7]; x[0]+=x[1];
x[0]^=x[1]<< 11; x[3]+=x[0]; x[1]+=x[2];
x[1]^=x[2]>> 2; x[4]+=x[1]; x[2]+=x[3];
x[2]^=x[3]<< 8; x[5]+=x[2]; x[3]+=x[4];
x[3]^=x[4]>> 16; x[6]+=x[3]; x[4]+=x[5];
x[4]^=x[5]<< 10; x[7]+=x[4]; x[5]+=x[6];
x[5]^=x[6]>> 4; x[0]+=x[5]; x[6]+=x[7];
x[6]^=x[7]<< 8; x[1]+=x[6]; x[7]+=x[0];
x[7]^=x[0]>> 9; x[2]+=x[7]; x[0]+=x[1];
}
private uint byteToIntLittle(
byte[] x,
int offset)
{
uint result = (byte) x[offset + 3];
result = (result << 8) | x[offset + 2];
result = (result << 8) | x[offset + 1];
result = (result << 8) | x[offset + 0];
return result;
}
private byte[] intToByteLittle(
uint x)
{
byte[] output = new byte[4];
output[3] = (byte)x;
output[2] = (byte)(x >> 8);
output[1] = (byte)(x >> 16);
output[0] = (byte)(x >> 24);
return output;
}
private byte[] intToByteLittle(
uint[] x)
{
byte[] output = new byte[4*x.Length];
for (int i = 0, j = 0; i < x.Length; i++,j+=4)
{
Array.Copy(intToByteLittle(x[i]), 0, output, j, 4);
}
return output;
}
}
}
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