C#使用RSA证书文件加密和解密

    public class EncrypHelp
    {
        static public byte[] RSAEncrypt(byte[] DataToEncrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
        {
            try
            {
                byte[] encryptedData;
                //Create a new instance of RSACryptoServiceProvider.
                using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
                {

                    //Import the RSA Key information. This only needs
                    //toinclude the public key information.
                    RSA.ImportParameters(RSAKeyInfo);

                    //Encrypt the passed byte array and specify OAEP padding.
                    //OAEP padding is only available on Microsoft Windows XP or
                    //later.
                    encryptedData = RSA.Encrypt(DataToEncrypt, DoOAEPPadding);
                }
                return encryptedData;
            }
            //Catch and display a CryptographicException
            //to the console.
            catch (CryptographicException e)
            {
                Console.WriteLine(e.Message);

                return null;
            }

        }

        static public byte[] RSADecrypt(byte[] DataToDecrypt, RSAParameters RSAKeyInfo, bool DoOAEPPadding)
        {
            try
            {
                byte[] decryptedData;
                //Create a new instance of RSACryptoServiceProvider.
                using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
                {
                    //Import the RSA Key information. This needs
                    //to include the private key information.
                    RSA.ImportParameters(RSAKeyInfo);

                    //Decrypt the passed byte array and specify OAEP padding.
                    //OAEP padding is only available on Microsoft Windows XP or
                    //later.
                    decryptedData = RSA.Decrypt(DataToDecrypt, DoOAEPPadding);
                }
                return decryptedData;
            }
            //Catch and display a CryptographicException
            //to the console.
            catch (CryptographicException e)
            {
                Console.WriteLine(e.ToString());

                return null;
            }

        }

        public static String Encrypt(String plaintext, X509Certificate2 pubcrt)
        {
            X509Certificate2 _X509Certificate2 = pubcrt;
            using (RSACryptoServiceProvider RSACryptography = _X509Certificate2.PublicKey.Key as RSACryptoServiceProvider)
            {
                Byte[] PlaintextData = Encoding.UTF8.GetBytes(plaintext);
                int MaxBlockSize = RSACryptography.KeySize / 8 - 11;    //加密块最大长度限制

                if (PlaintextData.Length <= MaxBlockSize)
                    return Convert.ToBase64String(RSACryptography.Encrypt(PlaintextData, false));

                using (MemoryStream PlaiStream = new MemoryStream(PlaintextData))
                using (MemoryStream CrypStream = new MemoryStream())
                {
                    Byte[] Buffer = new Byte[MaxBlockSize];
                    int BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);

                    while (BlockSize > 0)
                    {
                        Byte[] ToEncrypt = new Byte[BlockSize];
                        Array.Copy(Buffer, 0, ToEncrypt, 0, BlockSize);

                        Byte[] Cryptograph = RSACryptography.Encrypt(ToEncrypt, false);
                        CrypStream.Write(Cryptograph, 0, Cryptograph.Length);

                        BlockSize = PlaiStream.Read(Buffer, 0, MaxBlockSize);
                    }

                    return Convert.ToBase64String(CrypStream.ToArray(), Base64FormattingOptions.None);
                }
            }
        }

        public static String Decrypt(String ciphertext, X509Certificate2 prvpfx)
        {
            X509Certificate2 _X509Certificate2 = prvpfx;
            using (RSACryptoServiceProvider RSACryptography = _X509Certificate2.PrivateKey as RSACryptoServiceProvider)
            {
                Byte[] CiphertextData = Convert.FromBase64String(ciphertext);
                int MaxBlockSize = RSACryptography.KeySize / 8;    //解密块最大长度限制

                if (CiphertextData.Length <= MaxBlockSize)
                    return Encoding.UTF8.GetString(RSACryptography.Decrypt(CiphertextData, false));

                using (MemoryStream CrypStream = new MemoryStream(CiphertextData))
                using (MemoryStream PlaiStream = new MemoryStream())
                {
                    Byte[] Buffer = new Byte[MaxBlockSize];
                    int BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);

                    while (BlockSize > 0)
                    {
                        Byte[] ToDecrypt = new Byte[BlockSize];
                        Array.Copy(Buffer, 0, ToDecrypt, 0, BlockSize);

                        Byte[] Plaintext = RSACryptography.Decrypt(ToDecrypt, false);
                        PlaiStream.Write(Plaintext, 0, Plaintext.Length);

                        BlockSize = CrypStream.Read(Buffer, 0, MaxBlockSize);
                    }

                    return Encoding.UTF8.GetString(PlaiStream.ToArray());
                }
            }
        }

        private static X509Certificate2 RetrieveX509Certificate()
        {
            return null;    //检索用于 RSA 加密的 X509Certificate2 证书
        }

        //调用方法

        public void doit()
        {

            //Create a UnicodeEncoder to convert between byte array and string.
            UnicodeEncoding ByteConverter = new UnicodeEncoding();

            //Create byte arrays to hold original, encrypted, and decrypted data.
            byte[] dataToEncrypt = ByteConverter.GetBytes("310991");
            byte[] encryptedData;
            byte[] decryptedData;

            X509Certificate2 pubcrt = new X509Certificate2(AppDomain.CurrentDomain.BaseDirectory + "cmb.cer");
            RSACryptoServiceProvider pubkey = (RSACryptoServiceProvider)pubcrt.PublicKey.Key;
            //X509Certificate2 prvcrt = new X509Certificate2(AppDomain.CurrentDomain.BaseDirectory + "bfkey.pfx", "123456789", X509KeyStorageFlags.Exportable);
            //RSACryptoServiceProvider prvkey = (RSACryptoServiceProvider)prvcrt.PrivateKey;

            encryptedData = EncrypHelp.RSAEncrypt(dataToEncrypt, pubkey.ExportParameters(false), false);
            string encryptedDataStr = Convert.ToBase64String(encryptedData);
            Console.WriteLine("Encrypted plaintext: {0}", Convert.ToBase64String(encryptedData));

            //decryptedData = EncrypHelp.RSADecrypt(encryptedData, prvkey.ExportParameters(true), false);
            //Console.WriteLine("Decrypted plaintext: {0}", ByteConverter.GetString(decryptedData));

            //加密长内容
            String data = @"RSA 是常用的非对称加密算法。最近使用时却出现了“不正确的长度”的异常，研究发现是由于待加密的数据超长所致。
　　                    .NET Framework 中提供的 RSA 算法规定：
　　                    待加密的字节数不能超过密钥的长度值除以 8 再减去 11（即：RSACryptoServiceProvider.KeySize / 8 - 11），而加密后得到密文的字节数，正好是密钥的长度值除以 8（即：RSACryptoServiceProvider.KeySize / 8）。
　　                    所以，如果要加密较长的数据，则可以采用分段加解密的方式，实现方式如下：";

            string encrypt = EncrypHelp.Encrypt(data, pubcrt);
            Console.WriteLine("Encrypted plaintext: {0}", encrypt);
            //string decrypt = EncrypHelp.Decrypt(encrypt, prvcrt);
            //Console.WriteLine("Decrypted plaintext: {0}", decrypt);

            //prvkey.Clear();
            pubkey.Clear();
            Console.Read();

        }
    }