RSA加密方法

/// <summary>
        /// RSA加密
        /// </summary>
        /// <param name="data"></param>
        /// <param name="privateKey"></param>
        /// <returns></returns>

        public static string RSASignCharSet(string data, string privateKey)
        {

            byte[] signatureBytes = null;

            RSACryptoServiceProvider rsaCsp = LoadCertificateString(privateKey, "");

            byte[] dataBytes = Encoding.UTF8.GetBytes(data);

            signatureBytes = rsaCsp.SignData(dataBytes, "SHA256");
            return Convert.ToBase64String(signatureBytes);
        }

        private static RSACryptoServiceProvider LoadCertificateString(string strKey, string signType)
        {
            byte[] data = null;
            //讀取帶
            //ata = Encoding.Default.GetBytes(strKey);
            data = Convert.FromBase64String(strKey);
            //data = GetPem("RSA PRIVATE KEY", data);
            try
            {
                RSACryptoServiceProvider rsa = DecodeRSAPrivateKey(data, signType);
                return rsa;
            }
            catch (Exception ex)
            {
                //    throw new AopException("EncryptContent = woshihaoren,zheshiyigeceshi,wanerde", ex);
            }
            return null;
        }

        private static RSACryptoServiceProvider DecodeRSAPrivateKey(byte[] privkey, string signType)
        {
            byte[] MODULUS, E, D, P, Q, DP, DQ, IQ;

            // --------- Set up stream to decode the asn.1 encoded RSA private key ------
            MemoryStream mem = new MemoryStream(privkey);
            BinaryReader binr = new BinaryReader(mem);  //wrap Memory Stream with BinaryReader for easy reading
            byte bt = 0;
            ushort twobytes = 0;
            int elems = 0;
            try
            {
                twobytes = binr.ReadUInt16();
                if (twobytes == 0x8130) //data read as little endian order (actual data order for Sequence is 30 81)
                    binr.ReadByte();    //advance 1 byte
                else if (twobytes == 0x8230)
                    binr.ReadInt16();    //advance 2 bytes
                else
                    return null;

                twobytes = binr.ReadUInt16();
                if (twobytes != 0x0102) //version number
                    return null;
                bt = binr.ReadByte();
                if (bt != 0x00)
                    return null;


                //------ all private key components are Integer sequences ----
                elems = GetIntegerSize(binr);
                MODULUS = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                E = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                D = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                P = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                Q = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                DP = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                DQ = binr.ReadBytes(elems);

                elems = GetIntegerSize(binr);
                IQ = binr.ReadBytes(elems);


                // ------- create RSACryptoServiceProvider instance and initialize with public key -----
                CspParameters CspParameters = new CspParameters();
                CspParameters.Flags = CspProviderFlags.UseMachineKeyStore;

                int bitLen = 1024;
                if ("RSA2".Equals(signType))
                {
                    bitLen = 2048;
                }

                RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(bitLen, CspParameters);
                RSAParameters RSAparams = new RSAParameters();
                RSAparams.Modulus = MODULUS;
                RSAparams.Exponent = E;
                RSAparams.D = D;
                RSAparams.P = P;
                RSAparams.Q = Q;
                RSAparams.DP = DP;
                RSAparams.DQ = DQ;
                RSAparams.InverseQ = IQ;
                RSA.ImportParameters(RSAparams);
                return RSA;
            }
            catch (Exception ex)
            {
                return null;
            }
            finally
            {
                binr.Close();
            }
        }

        private static int GetIntegerSize(BinaryReader binr)
        {
            byte bt = 0;
            byte lowbyte = 0x00;
            byte highbyte = 0x00;
            int count = 0;
            bt = binr.ReadByte();
            if (bt != 0x02)        //expect integer
                return 0;
            bt = binr.ReadByte();

            if (bt == 0x81)
                count = binr.ReadByte();    // data size in next byte
            else
                if (bt == 0x82)
                {
                    highbyte = binr.ReadByte();    // data size in next 2 bytes
                    lowbyte = binr.ReadByte();
                    byte[] modint = { lowbyte, highbyte, 0x00, 0x00 };
                    count = BitConverter.ToInt32(modint, 0);
                }
                else
                {
                    count = bt;        // we already have the data size
                }

            while (binr.ReadByte() == 0x00)
            {    //remove high order zeros in data
                count -= 1;
            }
            binr.BaseStream.Seek(-1, SeekOrigin.Current);        //last ReadByte wasn't a removed zero, so back up a byte
            return count;
        }