namespace Encryption
{
    public class CEncryptServer
    {
        static int m_nPos1, m_nPos2;

        void Init()
        {
            m_nPos1 = m_nPos2 = 0; new CEncryptCode();
        }

        public class CEncryptCode
        {
            static Byte[] m_bufEncrypt1 = new Byte[256], m_bufEncrypt2 = new Byte[256];

            int aa = 0x7E,
             bb = 0x33,
             cc = 0xA1;
            ulong key1, key2;

            public CEncryptCode() { Init(); }
            void Init()
            {
                int a1, b1, c1, fst1;
                a1 = (int)((key1 >> 0) & 0xFF) ^ aa;
                b1 = (int)((key1 >> 8) & 0xFF) ^ bb;
                c1 = (int)((key1 >> 24) & 0xFF) ^ cc;
                fst1 = (int)(key1 >> 16) & 0xFF;

                int a2, b2, c2, fst2;
                a2 = (int)((key2 >> 0) & 0xFF) ^ aa;
                b2 = (int)((key2 >> 8) & 0xFF) ^ bb;
                c2 = (int)((key2 >> 24) & 0xFF) ^ cc;
                fst2 = (int)(key2 >> 16) & 0xFF;

                Byte nCode = (Byte)fst1;
                for (int i = 0; i < 256; i++)
                {
                    m_bufEncrypt1[i] = nCode;
                    nCode = (Byte)((a1 * nCode * nCode + b1 * nCode + c1) % 256);
                }
                Debug.Assert(nCode == fst1);

                nCode = (Byte)fst2;
                for (int i = 0; i < 256; i++)
                {
                    m_bufEncrypt2[i] = (Byte)nCode;
                    nCode = (Byte)((a2 * nCode * nCode + b2 * nCode + c2) % 256);
                }
                Debug.Assert(nCode == fst2);
            }
            void Encrypt(Byte[] bufMsg, int nLen, bool bMove)
            {
                int nOldPos1 = m_nPos1;
                int nOldPos2 = m_nPos2;
                for (int i = 0; i < nLen; i++)
                {
                    bufMsg[i] ^= m_bufEncrypt1[m_nPos1];
                    bufMsg[i] ^= m_bufEncrypt2[m_nPos2];

                    if (++m_nPos1 >= 256)
                    {
                        m_nPos1 = 0;
                        if (++m_nPos2 >= 256)
                            m_nPos2 = 0;
                    }
                    Debug.Assert(m_nPos1 >= 0 && m_nPos1 < 256);
                    Debug.Assert(m_nPos2 >= 0 && m_nPos2 < 256);
                }

                if (!bMove)
                {
                    m_nPos1 = nOldPos1;
                    m_nPos2 = nOldPos2;
                }
            }

            unsafe void ChangeCode(UInt32 dwData)
            {
                UInt32 dwData2 = dwData * dwData;
                for (int i = 0; i < 256; i += 4)
                {
                    *(UInt32*)(m_bufEncrypt1[i]) ^= dwData;
                    *(UInt32*)(m_bufEncrypt2[i]) ^= dwData2;
                }
            }
        }
    }

}