How to download over https

[matthew <matthew@mdavis.xyz>]

I'm trying to download an iso for installation.
The image I want is here:
http://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/
8.5.0-live+nonfree/amd64/iso-hybrid/

In particular I'm wanting debian-live-8.5.0-amd64-cinnamon-desktop+nonfree.iso 

However that's a http link. It I add an 's' into that url to make it https, I 
get an error saying the resource is unreachable. This is true of both the 
directory in the browser, the .iso in the browser, and the .iso with wget.

There are MD5 and SHA sums in that same directory. However I can only access 
those checksums through unencrypted connections. Therefore they cannot be used 
to check against 3rd party tampering. (Since someone who has the ability to 
tamper with the .iso can also tamper with the .txt files.)

Am I supposed to be able to use https? If not, how can I download debian iso 
files securely?