367 lines
9.0 KiB
C#
367 lines
9.0 KiB
C#
#if !BESTHTTP_DISABLE_ALTERNATE_SSL && (!UNITY_WEBGL || UNITY_EDITOR)
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#pragma warning disable
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using System;
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using System.Text;
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using BestHTTP.SecureProtocol.Org.BouncyCastle.Crypto.Parameters;
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using BestHTTP.SecureProtocol.Org.BouncyCastle.Crypto.Utilities;
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using BestHTTP.SecureProtocol.Org.BouncyCastle.Utilities;
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namespace BestHTTP.SecureProtocol.Org.BouncyCastle.Crypto.Engines
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{
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/// <summary>
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/// Implementation of Daniel J. Bernstein's Salsa20 stream cipher, Snuffle 2005
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/// </summary>
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public class Salsa20Engine
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: IStreamCipher
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{
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public static readonly int DEFAULT_ROUNDS = 20;
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/** Constants */
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private const int StateSize = 16; // 16, 32 bit ints = 64 bytes
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private readonly static uint[] TAU_SIGMA = Pack.LE_To_UInt32(Strings.ToAsciiByteArray("expand 16-byte k" + "expand 32-byte k"), 0, 8);
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internal void PackTauOrSigma(int keyLength, uint[] state, int stateOffset)
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{
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int tsOff = (keyLength - 16) / 4;
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state[stateOffset] = TAU_SIGMA[tsOff];
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state[stateOffset + 1] = TAU_SIGMA[tsOff + 1];
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state[stateOffset + 2] = TAU_SIGMA[tsOff + 2];
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state[stateOffset + 3] = TAU_SIGMA[tsOff + 3];
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}
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[Obsolete]
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protected readonly static byte[]
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sigma = Strings.ToAsciiByteArray("expand 32-byte k"),
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tau = Strings.ToAsciiByteArray("expand 16-byte k");
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protected int rounds;
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/*
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* variables to hold the state of the engine
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* during encryption and decryption
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*/
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private int index = 0;
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internal uint[] engineState = new uint[StateSize]; // state
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internal uint[] x = new uint[StateSize]; // internal buffer
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private byte[] keyStream = new byte[StateSize * 4]; // expanded state, 64 bytes
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private bool initialised = false;
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/*
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* internal counter
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*/
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private uint cW0, cW1, cW2;
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/// <summary>
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/// Creates a 20 round Salsa20 engine.
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/// </summary>
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public Salsa20Engine()
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: this(DEFAULT_ROUNDS)
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{
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}
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/// <summary>
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/// Creates a Salsa20 engine with a specific number of rounds.
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/// </summary>
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/// <param name="rounds">the number of rounds (must be an even number).</param>
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public Salsa20Engine(int rounds)
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{
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if (rounds <= 0 || (rounds & 1) != 0)
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{
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throw new ArgumentException("'rounds' must be a positive, even number");
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}
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this.rounds = rounds;
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}
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public virtual void Init(
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bool forEncryption,
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ICipherParameters parameters)
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{
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/*
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* Salsa20 encryption and decryption is completely
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* symmetrical, so the 'forEncryption' is
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* irrelevant. (Like 90% of stream ciphers)
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*/
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ParametersWithIV ivParams = parameters as ParametersWithIV;
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if (ivParams == null)
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throw new ArgumentException(AlgorithmName + " Init requires an IV", "parameters");
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byte[] iv = ivParams.GetIV();
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if (iv == null || iv.Length != NonceSize)
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throw new ArgumentException(AlgorithmName + " requires exactly " + NonceSize + " bytes of IV");
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ICipherParameters keyParam = ivParams.Parameters;
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if (keyParam == null)
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{
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if (!initialised)
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throw new InvalidOperationException(AlgorithmName + " KeyParameter can not be null for first initialisation");
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SetKey(null, iv);
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}
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else if (keyParam is KeyParameter)
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{
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SetKey(((KeyParameter)keyParam).GetKey(), iv);
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}
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else
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{
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throw new ArgumentException(AlgorithmName + " Init parameters must contain a KeyParameter (or null for re-init)");
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}
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Reset();
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initialised = true;
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}
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protected virtual int NonceSize
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{
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get { return 8; }
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}
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public virtual string AlgorithmName
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{
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get
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{
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string name = "Salsa20";
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if (rounds != DEFAULT_ROUNDS)
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{
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name += "/" + rounds;
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}
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return name;
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}
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}
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public virtual byte ReturnByte(
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byte input)
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{
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if (LimitExceeded())
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{
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throw new MaxBytesExceededException("2^70 byte limit per IV; Change IV");
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}
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if (index == 0)
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{
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GenerateKeyStream(keyStream);
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AdvanceCounter();
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}
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byte output = (byte)(keyStream[index] ^ input);
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index = (index + 1) & 63;
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return output;
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}
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protected virtual void AdvanceCounter()
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{
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if (++engineState[8] == 0)
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{
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++engineState[9];
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}
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}
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public virtual void ProcessBytes(
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byte[] inBytes,
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int inOff,
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int len,
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byte[] outBytes,
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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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Check.DataLength(inBytes, inOff, len, "input buffer too short");
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Check.OutputLength(outBytes, outOff, len, "output buffer too short");
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if (LimitExceeded((uint)len))
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throw new MaxBytesExceededException("2^70 byte limit per IV would be exceeded; Change IV");
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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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GenerateKeyStream(keyStream);
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AdvanceCounter();
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}
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outBytes[i+outOff] = (byte)(keyStream[index]^inBytes[i+inOff]);
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index = (index + 1) & 63;
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}
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}
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public virtual void Reset()
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{
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index = 0;
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ResetLimitCounter();
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ResetCounter();
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}
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protected virtual void ResetCounter()
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{
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engineState[8] = engineState[9] = 0;
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}
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protected virtual void SetKey(byte[] keyBytes, byte[] ivBytes)
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{
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if (keyBytes != null)
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{
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if ((keyBytes.Length != 16) && (keyBytes.Length != 32))
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throw new ArgumentException(AlgorithmName + " requires 128 bit or 256 bit key");
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int tsOff = (keyBytes.Length - 16) / 4;
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engineState[0] = TAU_SIGMA[tsOff];
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engineState[5] = TAU_SIGMA[tsOff + 1];
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engineState[10] = TAU_SIGMA[tsOff + 2];
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engineState[15] = TAU_SIGMA[tsOff + 3];
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// Key
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Pack.LE_To_UInt32(keyBytes, 0, engineState, 1, 4);
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Pack.LE_To_UInt32(keyBytes, keyBytes.Length - 16, engineState, 11, 4);
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}
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// IV
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Pack.LE_To_UInt32(ivBytes, 0, engineState, 6, 2);
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}
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protected virtual void GenerateKeyStream(byte[] output)
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{
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SalsaCore(rounds, engineState, x);
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Pack.UInt32_To_LE(x, output, 0);
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}
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internal static void SalsaCore(int rounds, uint[] input, uint[] x)
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{
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if (input.Length != 16)
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throw new ArgumentException();
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if (x.Length != 16)
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throw new ArgumentException();
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if (rounds % 2 != 0)
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throw new ArgumentException("Number of rounds must be even");
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uint x00 = input[ 0];
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uint x01 = input[ 1];
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uint x02 = input[ 2];
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uint x03 = input[ 3];
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uint x04 = input[ 4];
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uint x05 = input[ 5];
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uint x06 = input[ 6];
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uint x07 = input[ 7];
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uint x08 = input[ 8];
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uint x09 = input[ 9];
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uint x10 = input[10];
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uint x11 = input[11];
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uint x12 = input[12];
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uint x13 = input[13];
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uint x14 = input[14];
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uint x15 = input[15];
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for (int i = rounds; i > 0; i -= 2)
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{
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x04 ^= R((x00+x12), 7);
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x08 ^= R((x04+x00), 9);
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x12 ^= R((x08+x04),13);
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x00 ^= R((x12+x08),18);
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x09 ^= R((x05+x01), 7);
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x13 ^= R((x09+x05), 9);
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x01 ^= R((x13+x09),13);
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x05 ^= R((x01+x13),18);
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x14 ^= R((x10+x06), 7);
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x02 ^= R((x14+x10), 9);
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x06 ^= R((x02+x14),13);
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x10 ^= R((x06+x02),18);
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x03 ^= R((x15+x11), 7);
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x07 ^= R((x03+x15), 9);
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x11 ^= R((x07+x03),13);
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x15 ^= R((x11+x07),18);
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x01 ^= R((x00+x03), 7);
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x02 ^= R((x01+x00), 9);
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x03 ^= R((x02+x01),13);
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x00 ^= R((x03+x02),18);
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x06 ^= R((x05+x04), 7);
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x07 ^= R((x06+x05), 9);
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x04 ^= R((x07+x06),13);
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x05 ^= R((x04+x07),18);
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x11 ^= R((x10+x09), 7);
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x08 ^= R((x11+x10), 9);
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x09 ^= R((x08+x11),13);
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x10 ^= R((x09+x08),18);
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x12 ^= R((x15+x14), 7);
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x13 ^= R((x12+x15), 9);
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x14 ^= R((x13+x12),13);
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x15 ^= R((x14+x13),18);
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}
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x[ 0] = x00 + input[ 0];
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x[ 1] = x01 + input[ 1];
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x[ 2] = x02 + input[ 2];
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x[ 3] = x03 + input[ 3];
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x[ 4] = x04 + input[ 4];
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x[ 5] = x05 + input[ 5];
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x[ 6] = x06 + input[ 6];
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x[ 7] = x07 + input[ 7];
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x[ 8] = x08 + input[ 8];
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x[ 9] = x09 + input[ 9];
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x[10] = x10 + input[10];
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x[11] = x11 + input[11];
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x[12] = x12 + input[12];
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x[13] = x13 + input[13];
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x[14] = x14 + input[14];
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x[15] = x15 + input[15];
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}
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/**
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* Rotate left
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*
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* @param x value to rotate
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* @param y amount to rotate x
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*
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* @return rotated x
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*/
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internal static uint R(uint x, int y)
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{
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return (x << y) | (x >> (32 - y));
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}
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private void ResetLimitCounter()
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{
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cW0 = 0;
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cW1 = 0;
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cW2 = 0;
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}
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private bool LimitExceeded()
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{
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if (++cW0 == 0)
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{
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if (++cW1 == 0)
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{
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return (++cW2 & 0x20) != 0; // 2^(32 + 32 + 6)
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}
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}
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return false;
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}
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/*
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* this relies on the fact len will always be positive.
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*/
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private bool LimitExceeded(
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uint len)
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{
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uint old = cW0;
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cW0 += len;
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if (cW0 < old)
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{
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if (++cW1 == 0)
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{
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return (++cW2 & 0x20) != 0; // 2^(32 + 32 + 6)
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}
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}
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return false;
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}
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}
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}
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#pragma warning restore
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#endif
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