非对称加密

            string outPutString = null;
            string prikey;
            string pubkey;
            bool isSeccess = false;
            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                // 公钥 
                pubkey = rsa.ToXmlString(false);

                // 私钥 
                prikey = rsa.ToXmlString(true);

            }
            //私钥串+特征码生成 鬼画符
            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsa.FromXmlString(prikey);
                // 加密对象 
                RSAPKCS1SignatureFormatter f = new RSAPKCS1SignatureFormatter(rsa);
                f.SetHashAlgorithm("SHA1");
                byte[] source = System.Text.ASCIIEncoding.ASCII.GetBytes("878");
                SHA1Managed sha = new SHA1Managed();
                byte[] result = sha.ComputeHash(source);

                byte[] b = f.CreateSignature(result);

                outPutString = Convert.ToBase64String(b);
            }

            //公钥串+特征码+鬼画符  解码.
            using (RSACryptoServiceProvider rsa = new RSACryptoServiceProvider())
            {
                rsa.FromXmlString(pubkey);
                RSAPKCS1SignatureDeformatter f = new RSAPKCS1SignatureDeformatter(rsa);

                f.SetHashAlgorithm("SHA1");

                byte[] key = Convert.FromBase64String(outPutString);

                SHA1Managed sha = new SHA1Managed();
                byte[] name = sha.ComputeHash(ASCIIEncoding.ASCII.GetBytes("878"));
                if (f.VerifySignature(name, key))
                    isSeccess = true;
                else
                    isSeccess = false;
            }