KSM128.cs

Re-Work of the Sha3 Keccak Sponge for 128 Bit Hashing

using System;
using System.Runtime.CompilerServices;
public class KSM128 : HashAlgorithmEx
{
    private readonly int _outputLength;
    private readonly int _rateBytes;
    private readonly ulong[] _roundConstants =
    {
        0x0000000000000001,
        0x0000000000008082,
        0x800000000000808A,
        0x8000000080008000,
        0x000000000000808B,
        0x0000000080000001,
        0x8000000080008081,
        0x8000000000008009,
        0x000000000000008A,
        0x0000000000000088,
        0x0000000080008009,
        0x000000008000000A,
        0x000000008000808B,
        0x800000000000008B,
        0x8000000000008089,
        0x8000000000008003,
        0x8000000000008002,
        0x8000000000000080,
        0x000000000000800A,
        0x800000008000000A,
        0x8000000080008081,
        0x8000000000008080,
        0x0000000080000001,
        0x8000000080008008
    };
    private readonly ulong[] _seed;
    private          int     _blockSize;
    private          int     _input;
    private          int     _output;
    private          byte[]  _result;
    private          ulong[] _state;
    public           int     HashLength;
    public           int     Rounds = 24;
    public KSM128(int size, int rounds = 24, ulong[] seed = null)
    {
        if (rounds > 24)
            throw new Exception($"Maximum rounds allowed is {24}");
        var MaxBR     = (64 >> 3) * 5;
        var sizeBytes = size >> 3;
        var rateBytes = MaxBR - (sizeBytes << 1);
        var MaxSize   = ((MaxBR - 8)       >> 1) << 3;
        if (rateBytes < 8)
            throw new Exception($"Maximum size allowed is {MaxSize} Bits with {128} bit Width specified. Specified Size is {size} Bits.");
        var outputLength = size >> 3;
        _rateBytes    = rateBytes;
        _outputLength = outputLength;
        HashLength    = outputLength;
        _seed         = seed;
    }
    public override void Initialize()
    {
        _blockSize = 0;
        _input     = 0;
        _output    = 0;
        _state     = new ulong[5];
        _result    = new byte[_outputLength];
        if (_seed != null && _seed[0] != 0)
        {
            for (var i = 0; i < _seed.Length && i < _state.Length; ++i)
                _state[i] = _seed[i];
            Permute(_state);
        }
    }
    public void Absorb(byte[] array, int start, int size)
    {
        while (size > 0)
        {
            _blockSize = Math.Min(size, _rateBytes);
            for (var index = start; index < _blockSize; ++index)
            {
                var num = Convert.ToByte(Buffer.GetByte(_state, index) ^ array[index + _input]);
                Buffer.SetByte(_state, index, num);
            }
            _input += _blockSize;
            size   -= _blockSize;
            if (_blockSize == _rateBytes)
            {
                Permute(_state);
                _blockSize = 0;
            }
        }
    }
    public byte[] Squeeze()
    {
        Buffer.SetByte(_state, _blockSize,     Convert.ToByte(Buffer.GetByte(_state, _blockSize)     ^ 6));
        Buffer.SetByte(_state, _rateBytes - 1, Convert.ToByte(Buffer.GetByte(_state, _rateBytes - 1) ^ 128));
        Permute(_state);
        var outputLength = _outputLength;
        while (outputLength > 0)
        {
            _blockSize = Math.Min(outputLength, _rateBytes);
            Buffer.BlockCopy(_state, 0, _result, _output, _blockSize);
            _output      += _blockSize;
            outputLength -= _blockSize;
            if (outputLength > 0)
                Permute(_state);
        }
        return _result;
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private void Permute(ulong[] state)
    {
        for (var round = 0; round < Rounds; ++round)
        {
            Theta(out var C0, state, out var C1, out var C2, out var C3, out var C4);
            RhoPi(state);
            Chi(ref C0, state, ref C1, ref C2, ref C3, ref C4);
            Iota(round, state);
        }
    }
    private static void Theta(out ulong C0, ulong[] state, out ulong C1, out ulong C2, out ulong C3, out ulong C4)
    {
        C0 = state[0] ^ state[4];
        C1 = state[1] ^ state[0];
        C2 = state[2] ^ state[1];
        C3 = state[3] ^ state[2];
        C4 = state[4] ^ state[3];
        var D0 = Rol(C1, 1) ^ C4;
        var D1 = Rol(C2, 1) ^ C0;
        var D2 = Rol(C3, 1) ^ C1;
        var D3 = Rol(C4, 1) ^ C2;
        var D4 = Rol(C0, 1) ^ C3;
        state[0] ^= D0;
        state[1] ^= D1;
        state[2] ^= D2;
        state[3] ^= D3;
        state[4] ^= D4;
    }
    private static void RhoPi(ulong[] state)
    {
        var a = Rol(state[1], 1);
        state[1] = Rol(state[4], 44);
        state[4] = Rol(state[3], 43);
        state[3] = Rol(state[2], 14);
        state[4] = Rol(state[1], 21);
        state[2] = a;
    }
    private void Iota(int round, ulong[] state)
    {
        state[0] ^= _roundConstants[round];
    }
    private static void Chi(ref ulong C0, ulong[] state, ref ulong C1, ref ulong C2, ref ulong C3, ref ulong C4)
    {
        C0       = state[0] ^ (~state[1] & state[2]);
        C1       = state[1] ^ (~state[2] & state[3]);
        C2       = state[2] ^ (~state[3] & state[4]);
        C3       = state[3] ^ (~state[4] & state[0]);
        C4       = state[4] ^ (~state[0] & state[1]);
        state[0] = C0;
        state[1] = C1;
        state[2] = C2;
        state[3] = C3;
        state[4] = C4;
    }
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    private static ulong Rol(ulong x, byte y)
    {
        return (x << y) | (x >> (64 - y));
    }
    protected override void HashCore(byte[] array, int ibStart, int cbSize)
    {
        Initialize();
        Absorb(array, ibStart, cbSize);
    }
    protected override byte[] HashFinal()
    {
        return Squeeze();
    }
}