I faced similar error and after a days debugging.. it got fixed when I added the $key directly in the code. It seems that the single line textbox in the UI is not accepting a multi-line public key and it ends up throwing error in openssl_verify.
I had also a requirement where the User should be browsed to the requested URL (which can vary) after Auto Login, but there is no such setting and I had to modify the code to accept Query String parameter to redirect.
But once its done it works awesome.
Thanks
-Sachin.
