为啥我不能使用 RijndaelManaged 解密数据？

Posted 2023-02-22

【中文标题】为啥我不能使用 RijndaelManaged 解密数据？

【英文标题】：Why can't I decrypt data using RijndaelManaged?为什么我不能使用 RijndaelManaged 解密数据？

【发布时间】：2011-11-10 15:09:00

【问题描述】：

我正在开发一个像信使一样发送和接收消息的程序，我需要在发送按钮上加密消息并在收到消息时解密消息。我正在使用 RijndaelManaged 类和以下方法来加密/解密

 public byte[] EncryptStringToBytes(string plainText, byte[] Key, byte[] IV)
    

        // Check arguments.
        if (plainText == null || plainText.Length <= 0)
            throw new ArgumentNullException("plainText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("Key");
        byte[] encrypted;
        // Create an RijndaelManaged object
        // with the specified key and IV.
        using (RijndaelManaged rijAlg = new RijndaelManaged())
        
            rijAlg.Key = Key;
            rijAlg.IV = IV;

            // Create a decrytor to perform the stream transform.
            ICryptoTransform encryptor = rijAlg.CreateEncryptor(rijAlg.Key, rijAlg.IV);

            // Create the streams used for encryption.
            using (MemoryStream msEncrypt = new MemoryStream())
            
                using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
                
                    using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                    

                        //Write all data to the stream.
                        swEncrypt.Write(plainText);
                    
                    encrypted = msEncrypt.ToArray();

                
            
        


        // Return the encrypted bytes from the memory stream.
        return encrypted;

    

和

 public string DecryptStringFromBytes(byte[] cipherText, byte[] Key, byte[] IV)
    
        // Check arguments.
        if (cipherText == null || cipherText.Length <= 0)
            throw new ArgumentNullException("cipherText");
        if (Key == null || Key.Length <= 0)
            throw new ArgumentNullException("Key");
        if (IV == null || IV.Length <= 0)
            throw new ArgumentNullException("Key");

        // Declare the string used to hold
        // the decrypted text.
        string plaintext = null;

        // Create an RijndaelManaged object
        // with the specified key and IV.
        using (RijndaelManaged rijAlg = new RijndaelManaged())
        
            rijAlg.Key = Key;
            rijAlg.IV = IV;

            // Create a decrytor to perform the stream transform.
            ICryptoTransform decryptor = rijAlg.CreateDecryptor(rijAlg.Key, rijAlg.IV);

            // Create the streams used for decryption.
            using (MemoryStream msDecrypt = new MemoryStream(cipherText))
            
                using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, decryptor, CryptoStreamMode.Read))
                
                    using (StreamReader srDecrypt = new StreamReader(csDecrypt))
                    

                        // Read the decrypted bytes from the decrypting stream
                        // and place them in a string.
                        plaintext = srDecrypt.ReadToEnd();
                    
                
            

        

        return plaintext;

    

这是我调用之前方法的方式：

  private void SendMessage()
    
        string str;

        System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding();
        str = enc.GetString(this.EncryptStringToBytes(this.txtNewMessage.Text, myRijndael.Key, myRijndael.IV ));

        if ( this.remoteClient.Connected && this.txtNewMessage.Text.Trim() != "")
        
            this.remoteClient.SendCommand(new Proshot.CommandClient.Command(Proshot.CommandClient.CommandType.Message, this.targetIP,str));
            this.txtMessages.Text += this.remoteClient.NetworkName + ": " + this.txtNewMessage.Text.Trim()  + "//---SENT" + Environment.NewLine;
            this.txtNewMessage.Text = "";
            this.txtNewMessage.Focus();
        
    



  private void private_CommandReceived(object sender , CommandEventArgs e)
    
        string str;
        byte[] byteString;


        str =  e.Command.MetaData;

        System.Text.UTF8Encoding encoding = new System.Text.UTF8Encoding();
        byteString = encoding.GetBytes(str);


        switch ( e.Command.CommandType )
        
            case ( CommandType.Message ):
                if ( !e.Command.Target.Equals(IPAddress.Broadcast) && e.Command.SenderIP.Equals(this.targetIP))
                
                    //myRijndael.Padding = PaddingMode.Zeros;
                    this.txtMessages.Text += e.Command.SenderName + ": " + this.DecryptStringFromBytes(byteString, myRijndael.Key, myRijndael.IV) + "//---Received" + Environment.NewLine;
                    if ( !this.activated)
                    
                        if(this.WindowState == FormWindowState.Normal || this.WindowState == FormWindowState.Maximized)
                            ShareUtils.PlaySound(ShareUtils.SoundType.NewMessageReceived);
                        else
                            ShareUtils.PlaySound(ShareUtils.SoundType.NewMessageWithPow);
                        this.Flash(this.Handle , FlashMode.FLASHW_ALL , 3);
                    
                
                break;
            
    

问题是我在解密时遇到异常加密异常 - 要解密的数据长度无效，我不知道为什么？

【参考方案1】：

在设置encrypted 字节数组之前，您可能应该在加密时刷新CryptoStream：

...
csEncrypt.FlushFinalBlock();
encrypted = msEncrypt.ToArray();
...

CryptoStream.FlushFinalBlock Method 的摘录：

调用 Close 方法将调用 FlushFinalBlock。如果你不打电话 关闭，调用 FlushFinalBlock 完成缓冲区的刷新。称呼 仅在所有流活动完成时才刷新FinalBlock。

显然，如果您调用Close，所有数据都将丢失，因为它也会关闭底层MemoryStream。