While working with SharePoint 2013 and ADFS I needed to perform encryption during the process. This is very easy to setup within ADFS, by editing the properties of the Relying Party to set the encryption certificate.

Once this is set and ADFS is enabled on the site, when you access the site you get an error with no error message. Upon looking in the event log I saw the following error.

This error is saying that SharePoint is unable to use the encryption key as it is unaware of the key itself. To resolve this we need to modify the web.config for SharePoint with the following: