Encrypt .NET Configuration File

Under some scenarios, developers want to encrypt some sections inside app.config or web.config file. This article How To: Encrypt Configuration Sections in ASP.NET 2.0 Using RSA describes how to do so clearly, Scott Guthrie also posted one: Encrypting Web.Config Values in ASP.NET 2.0.

However, in the posts above, they use aspnet_regiis.exe and it seems it doesn’t directly support app.config, if we want to encrypt app.config for Windows Form or WPF applications While I tried use it to encrypt my app.config file, it generates a web.config which means my Winform definitely can’t use it, even if I copy the encrypted appSettings section from this generated web.config to my own app.config (ConfigurationManager.AppSettings[EncryptedKeyName] is null after I did that).

After several minutes of Google search and testing, I found the code below is simple and very straight forward to achieve this:

Configuration config = ConfigurationManager.OpenExeConfiguration(
    ConfigurationUserLevel.None);

SectionInformation appSettingsSecInfo = config.GetSection(
   "appSettings").SectionInformation;
if (!appSettingsSecInfo.IsProtected)
{
    Console.WriteLine("The configuration file has NOT been protected!");

    // Encrypt this section by using security provider 
    // (RsaProtectedConfigurationProvider or DpapiProtectedConfigurationProvider).
    appSettingsSecInfo.ProtectSection("RsaProtectedConfigurationProvider");
    appSettingsSecInfo.ForceSave = true;

    config.Save(ConfigurationSaveMode.Full);
}

This code snippet will do the encryption job and works for both app.config/web.config. Here is the MSDN definition page for SectionInformation.ProtectSection.

References

• Overview of Protected Configuration: http://msdn.microsoft.com/en-us/library/hh8x3tas.aspx
• RsaProtectedConfigurationProvider Class:
• http://msdn.microsoft.com/en-us/library/system.configuration.rsaprotectedconfigurationprovider.aspx
• DpapiProtectedConfigurationProvider Class:
• http://msdn.microsoft.com/en-us/library/system.configuration.dpapiprotectedconfigurationprovider.aspx