file decryption using DES in asp.net

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ASP.NET

Hi,
This is my first post. I am trying to do file encryption and decryption using DES algorithm in ASP.Net with C#. I have successfully encrypted the file and uploaded it. When I download, the encrypted file will be available. Now, I need to decrypt the file by selecting the file through upload control. Can any one please help me?

The encryption code is below:

filename = Path.GetFileName(FileUpload1.PostedFile.FileName);

        System.IO.Stream myStream;
        Int32 fileLen;
        StringBuilder displayString = new StringBuilder();
        fileLen = FileUpload1.PostedFile.ContentLength;

        Byte[] Input = new Byte[fileLen];

        // Initialize the stream to read the uploaded file.
        myStream = FileUpload1.FileContent;

        // Read the file into the byte array.
        myStream.Read(Input, 0, fileLen);

        // Copy the byte array to a string.
        for (int loop1 = 0; loop1 < fileLen; loop1++)
        {
            displayString.Append(Input[loop1].ToString());
        }

        //TextBox1.Text = displayString.ToString();
        bytes = ASCIIEncoding.ASCII.GetBytes(dktxt.Text);
        bytes1 = ASCIIEncoding.ASCII.GetBytes(ck);
        
        string originalString = displayString.ToString();

        // DES algorithm to encrypt the given file
        DESCryptoServiceProvider cryptoProvider = new DESCryptoServiceProvider();
        MemoryStream memoryStream = new MemoryStream();
        CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoProvider.CreateEncryptor(bytes, bytes1), CryptoStreamMode.Write);
        StreamWriter writer = new StreamWriter(cryptoStream);
        writer.Write(originalString);
        writer.Flush();
        cryptoStream.FlushFinalBlock();
        writer.Flush();

        // store the encrypted data of a file
        cryptedString = Convert.ToBase64String(memoryStream.GetBuffer(), 0, (int)memoryStream.Length);