/// <summary>
/// Password string
/// </summary>
const string password = "some_password";
       
/// <summary>
/// Generates encryption Key based on the password
/// </summary>
/// <param name="keySize"></param>
/// <returns></returns>
public static byte[] GetEncryptionKey(int keySize)
{
    Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password,
 			 Encoding.ASCII.GetBytes(password.ToCharArray()));
    return key.GetBytes(keySize / 8);           
}

/// <summary>
/// Generates encryption IV based on the password
/// </summary>
/// <param name="blockSize"></param>
/// <returns></returns>
public static byte[] GetEncryptionIV(int blockSize)
{
    Rfc2898DeriveBytes key = new Rfc2898DeriveBytes(password, 
                   Encoding.ASCII.GetBytes(password.ToCharArray()));
    return key.GetBytes(blockSize / 8);
}

/// <summary>
/// Receives chunks of video file, encrypt them and save to disk
/// </summary>
/// <param name="objRequest">Instance of class UploadRequest</param>
[WebMethod]        
public void UploadVideo(UploadRequest objRequest)
{
    long length = 0;
    string tempUploadLocation = string.Format("C:\\temp\\{0}", 
 Path.GetFileName(objRequest.FileName));

    if (objRequest.FileBytes.Length > 0)
    {
        using (FileStream writer = new FileStream(tempUploadLocation, 
 File.Exists(tempUploadLocation) ? FileMode.Append : 
 FileMode.Create, FileAccess.Write))
        {
            RijndaelManaged rm = new RijndaelManaged();
            using (CryptoStream crStream = new CryptoStream(writer, 
		   			   rm.CreateEncryptor(EncryptionHelper.GetEncryptionKey(rm.KeySize),
                   			   EncryptionHelper.GetEncryptionIV(rm.BlockSize)), CryptoStreamMode.Write))
            {
                crStream.Write(objRequest.FileBytes, 0, objRequest.FileBytes.Length);
                length = writer.Length;
            }
        }
    }
    //// Check if file upload is complete
    if (length >= objRequest.FileSize)
    {
        //// Post upload processing goes here 
    }           
}

/// <summary>
/// Decrypt the file and save it to the temp location (Server)
/// </summary>
/// <param name="filePath"></param>
[WebMethod]
public string DecryptVideoAndSaveInTemp(string filePath)
{
    byte[] bytMedia = null;
    string tempDownloadLocation = string.Format("D:\\Temp\\{0}",Path.GetFileName(filePath));

    using (FileStream fs1 = File.Open(filePath, FileMode.Open, FileAccess.Read))
    {                
        RijndaelManaged rm = new RijndaelManaged();
        rm.Padding = PaddingMode.None;

        //// Decrypt the file
        using (CryptoStream cs = new CryptoStream(fs1, rm.CreateDecryptor(EncryptionHelper.GetEncryptionKey(rm.KeySize), EncryptionHelper.GetEncryptionIV(rm.BlockSize)), CryptoStreamMode.Read))
        {
            bytMedia = new byte[fs1.Length];
            Stream streamObject = cs;
            streamObject.Read(bytMedia, 0, (int)fs1.Length);
        }

        //// Use the decrypted byte array and save to the disk
        using (FileStream fs = new FileStream(tempDownloadLocation, FileMode.CreateNew))
        {
            fs.Write(bytMedia, 0, bytMedia.Length);
        }                
    }

    return string.Format("File decrypted and copied to {0}", tempDownloadLocation);
}

/// <summary>
/// Chunk the file and upload
/// </summary>
/// <param name="filename"></param>
private void UploadVideo(string filename)
{
    #region Vars
    const int chunkSize = 512000;
    byte[] bytes = null;
    int startIndex, endIndex, length, totalChunks;           

    WS.UploadRequest objRequest = new WS.UploadRequest();            
    #endregion

    try
    {
        if (File.Exists(filename))
        {
            using (WS.UploadService objService = new WS.UploadService())
            {
                using (FileStream fs = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read))
                {
                    //// Calculate total chunks to be sent to service
                    totalChunks = (int)Math.Ceiling((double)fs.Length / chunkSize);

                    //// Set up Upload request object
                    objRequest.FileName = filename;
                    objRequest.FileSize = fs.Length;
                            
                    for (int i = 0; i < totalChunks; i++)
                    {
                        startIndex = i * chunkSize;
                        endIndex = (int)(startIndex + chunkSize > fs.Length ? fs.Length : startIndex + chunkSize);
                        length = endIndex - startIndex;
                        bytes = new byte[length];

                        //// Read bytes from file, and send upload request
                        fs.Read(bytes, 0, bytes.Length);
                        objRequest.FileBytes = bytes;
                        objService.UploadVideo(objRequest);
                    }
                }

            }
        }
    }
    catch (Exception ex)
    {
        MessageBox.Show(string.Format("Error- {0}", ex.Message));
    }
}