In the documentation (http://docs.telerik.com/devtools/aspnet-ajax/controls/asyncupload/security) you can read "In order to encrypt the configuration in a secure way, we strongly recommend to set the custom encryption key in the web config using the following app setting -Telerik.AsyncUpload.ConfigurationEncryptionKey".
What kind of value can I set for the Telerik.AsyncUpload.ConfigurationEncryptionKey. Is it a random string? If yes how long it should be.