Lighning fast xor crypt

XoRCrypto.cs

using System.Runtime.CompilerServices;

namespace TestingEnv
{
    internal class XoRCrypto
    {
        private readonly int[] _keyChain;
        private int _ckey;

        public XoRCrypto(int[] chain = null)
        {
            _ckey = 0;
            _keyChain = chain ?? new[]
            {
                1234,
                2341,
                3412,
                4123,
                5555,
                3214,
                5656,
                1337
            };
        }

        public unsafe void Encrypt(byte[] buffer, int length = -1)
        {
            var iterations = 0;
            if (length == -1 || length > buffer.Length)
                length = buffer.Length / sizeof(int);
            else
                length = length / sizeof(int);

            var ikey = _keyChain[_ckey];

            fixed (byte* pBuf = buffer)
            {
                var asint = (int*)pBuf;

                for (var i = 0; i < length; i++)
                {
                    *asint ^= ikey + i;
                    asint++;
                    if (*asint % 100 == 0)
                    {
                        MoveNext();
                        ikey = _keyChain[_ckey];
                        iterations++;
                    }
                }
            }
            MoveNext();
        }

        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        private unsafe void MoveNext()
        {
            var cKey = _ckey;
            var cLen = _keyChain.Length;
            fixed (int* pInt = _keyChain)
            {
                var keyVal = pInt[cKey]; //*(pInt + cKey);

                for (var i = 0; i < cLen; i++)
                {
                    if (i == cKey)
                        continue;

                    pInt[i] += keyVal;
                    // *(pInt + i) += keyVal;
                }
            }

            if (cKey == cLen - 1)
                cKey = 0;
            else
                cKey++;

            _ckey = cKey;
        }
    }
}