Stunnel certificate; very basic questions

[dee]

My knowledge of networking is substantially lacking to the point where I need to clear up some very basic information and more importantly, my misconceptions. So please excuse it and thanks in advance for your highly valued responses.
I am just now recovering from a total re-install of Win 10, and Blue Iris. Stunnel is next.

I will be using an external DDNS from Asus in the form of https://xxxxxxxxxxxxx.asuscomm.com:8443.
I was issued a cert_key.tar file from Let's Encrypt Authority X3, which I assume is a certificate for my router only?
... or should this automatically cover everything that comes from my router. I have always been under the impression that if you connect to anything that starts with https:// in its URL, then it is already secure.

If I still need a separate certificate for the Blue Iris web server in the form of a .pem file, then can I use some information from the cert_key.tar file inside the .pem file that I will need to create?
I ask this because the expiration from cert_key.tar file comes with a renewal reminder and somewhat better reputation.

The Common Name (FQDN) should be the hostname of the machine running stunnel. (according to stunnel web site).
Would that be?
1. DESKTOP-83T0H6C (name of my computer)
2. 6D447D6E-C19F-4D77-A2F9-13DD22EA66FA (Device ID)
3. ?

 

[TL1096r]

This might help:

What are you using/doing to make your camera more secure?

Website used for SSL:
Free SSL Certificate Wizard and other SSL Tools @ ZeroSSL

See steps below to set this up:

After hours of frustration, finally solved it. I used the website Free SSL Certificate Wizard and other SSL Tools @ ZeroSSL to create a new self signed certificate, and put my no-ip domain as the domain. This generates key.txt and crt.txt files. You then open the old stunnel.pem file, and replace everything in the file using both the key.txt contents then the crt.txt contents in that order.

This includes replacing the -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY----- parts, as the new key from zerossl uses -----BEGIN RSA PRIVATE KEY----- and -----END RSA PRIVATE KEY----- instead.

It now works with both the updated version of chrome on my android phone, and chrome on my work computer.