I need to do a JWT to request authorization to Google. Because of the design, it will need to be done on a server script running on Rhino and I have no access to node.js. Google requires a RSA SHA-256 algorithm.
At this point I reach a big roadblock, not sure if I will ever be able to do this.
Thanks to Andre Werlang for the help.
Here is the library that works:
github.com/kjur/jsrsasign/blob/master/npm/lib/jsrsasign.js
Works like a charm: KJUR.jws.JWS.sign('RS256', header, claim, private_key);