It should be retina scans or handprints needed to register, that and a valid, checked SS# before the registration goes through. That way, if somebody tries to register under another SS#, the retina or handprint scan will pull up a name already registered thereby eliminating the possibility of registering twice under different SS#s.
Maybe a national database for this too. And when you goto the polls, you have to go to your pretedermined polling place, and have your hand or retina scanned again before you can fill out a ballot.
Of course, one political party or the other will claim this 'disenfranchises voters without eyes or hands' or some such thing.