This article does not apply to Umbraco 8.
The concepts and code in this article have been deprecated in Umbraco 8 and no longer apply.
If you are using Umbraco 7, this article is perfect for you!
This setting is replaced by
Umbraco.Core.UseHttps in v8.
Makes sure that all of the requests in the backoffice are called over HTTPS instead of HTTP when set to
<add key="umbracoUseSSL" value="true" />