Wordpress Integration

Anyone have any idea how to integrate the user information of wordpress and opencart together. That way ppl don't have to login twice with 2 separate accounts?

Make one login system the master and update the slave in real time or via a batch process.

Modify the login script for the slave to accept login details from the master somehow (possibly plugged into the session).

I'm guessing WP would be the best base for that? This sounds out of my league... Anyone need a job? lol