OAuth client for OSM

Hi all,
I’m interested in creating an Oauth 1.0 client for Openstreetmaps. I wanted to make my own client without using libraries. In OSM I saw that callback url is optional and have to set when registering application. But according to normal protocol we have to insert callback as a parameter.
oauthRequest(‘requestTokenURL’, ‘POST’, $parameters)

This $parameters variable only consists of ‘callback’ url.

In this case I’m confused about what should be included in parameter list that send to Request Token URL ?

Will it cause any problem if I send it as an empty variable ?

Thank you!

some oauth topics are already at http://help.openstreetmap.org … do a search there … maybe there are some hints?