Hello Thomas,
You can see the part of Implementation Guide below.
I am not sure whether it is must but it is the indication of SSL need.
"
SAP Single Sign-On 2.0 SP04
Document Version: 1.0 - 2014-10-28
Secure Login for SAP Single Sign-On Implementation Guide
1 What Is Secure Login?
Secure Login also provides single sign-on for Web browser access to the SAP Portal (and other HTTPS-enabled Web applications) with SSL.
"
Regards,
Yuksel AKCINAR