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