Posi-drive bit, it's basically the same as a phillips head, grab a #3 (I think) Posi bit or phillips bit and a drill, set the drill to high torque with a low speed, that should do it, just make sure you don't strip it out, then it's a real bitch.
yeah #3 is posi. it's basically a phillips , but it has 4 extra mini teeth/blade things that grab the posi screws used in binding better. and if you have an adjustable torque , go to drill and slow speed, obviously breaking the tightness with a handheld posi driver would be ideal
Little tip though... use it manually to take them off. If the screws are jammed and you have the wrong torque setting chances are you will strip the screw. Press down hard and twist. If you see you're starting to strip bring them to a shop before the heads are totalled.