C# FNV1a128 Implementation

FNV1a128.cs

    /// <summary>
    ///     No collisions with 20M random byte arrays. 32x slower than FNV1a64.
    ///     https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
    /// </summary>
    public class FNV1a128 : HashAlgorithm
    {
        private readonly BigInteger _K = "309485009821345068724781371".NewBigInteger10();
        private BigInteger _hash;
        private readonly BigInteger Seed = "144066263297769815596495629667062367629".NewBigInteger10();
        public FNV1a128()
        {
        }
        public FNV1a128(string seed)
        {
            Seed = seed.NewBigInteger10();
            Initialize();
        }
        public override int HashSize => 128;
        public override void Initialize()
        {
            _hash = Seed;
public class FNV1a128 : HashAlgorithm
    {
        private readonly BigInteger _K = "309485009821345068724781371".NewBigInteger10();
        private BigInteger _hash;
        private readonly BigInteger Seed = "144066263297769815596495629667062367629".NewBigInteger10();
        public FNV1a128()
        {
            _hash = Seed;
        }
        public FNV1a128(string seed)
        {
            Seed = seed.NewBigInteger10();
            _hash = Seed;
        }
        public override int HashSize => 128;
        public override void Initialize()
        {
            _hash = Seed;
        }
        protected override void HashCore(byte[] bytes, int ibStart, int cbSize)
        {
            Hash64(bytes, ibStart, cbSize);
        }
        private void Hash64(byte[] bytes, int ibStart, int cbSize)
        {
            if (bytes == null)
                return;
            if (ibStart >= bytes.Length || cbSize > bytes.Length)
                return;
            var p = 0;
            while (cbSize > 0)
            {
                _hash ^= bytes[p + ibStart];
                _hash *= _K;
                cbSize--;
                p++;
            }

            _hash = _hash ^ (_hash >> 64);
        }
        /// <summary>
        /// BigInteger does not overflow, so we limit the output to 128Bits.
        /// </summary>
        protected override byte[] HashFinal()
        {
            return _hash.ToByteArray().SubByte(0, 16);
        }
    }        }
        protected override void HashCore(byte[] bytes, int ibStart, int cbSize)
        {
            Hash64(bytes, ibStart, cbSize);
        }
        private void Hash64(byte[] bytes, int ibStart, int cbSize)
        {
            if (bytes == null)
                return;
            if (ibStart >= bytes.Length || cbSize > bytes.Length)
                return;
            var p = 0;
            while (cbSize > 0)
            {
                _hash ^= bytes[p + ibStart];
                _hash *= _K;
                cbSize--;
                p++;
            }

            _hash = _hash ^ (_hash >> 64);
        }
        /// <summary>
        /// BigInteger does not overflow, so we limit the output to 128Bits.
        /// </summary>
        protected override byte[] HashFinal()
        {
            return _hash.ToByteArray().SubByte(0, 16);
        }
    }