In regards to opening a door, Hardware: Electronics seems like the skill of choice in Eclipse Phase. However, I will allow you to use Infiltration at a -10 penalty or an Infosec roll with no penalty. Some complementary skills that could give you a +30 to the check if made could be Profession: Ego Hunter since you might have had experience opening locked doors with that, or Research to look up the schematics of the lock to get a better idea of how to open it. You can also use the Covert Operations Tool, but its likely that it will trigger an alarm on the building's network.
Other ways to open the door could be to talk to the landlord and make him open the door, or to use Networking to find someone who could open the door.