You might want to reconsider the viability of your idea if it can be stolen out right without your domain knowledge and connections and still be successful.
As a technical cofounder, this would be a major red flag for me if you were so secretive while building a relationship. It doesn't sound like you actually bring anything to the table. You should have connections, skills, and domain knowledge which would make it extremely difficult for someone to compete. If you don't have that, why would I want to work with you?