nginx with ssl as reverse proxy

[Ran Shalit]

Hello,

I have followed the article which explains how to configure nginx with
ssl as reverse proxy for Jenkins:
https://www.digitalocean.com/community/tutorials/how-to-configure-nginx-with-ssl-as-a-reverse-proxy-for-jenkins

Yet, I don't understand one thing,
The ssl key is configured only for nginx:

client ------- nginx proxy ----Jenkins server
                     <ssl key>

Doesn't Jenkins server need to be provided with keys too  ?

Thank you,
Ran