[ivraatiems]

If you can elaborate on (or show, but I realize that's legally hazy) the decompiled source, I think this should be possible to discern. I'd probably start by looking for anything in the source that looks like it's making any kind of network connection, then narrowing it down from there.

Typically, the response to authentication is a yes/no plus a token or other piece of session state for the authenticated app to store. You might poke through the structure of the in-app storage to see where the authentication information lives, and then go backwards from there to where it is set.

Edit: On a cursory google search, https://github.com/ryanseys/node-jawbone-up looks like it might help you.