Let's be honest here. It takes more than this: "Paper, pencil, optical scanner is all one needs to run an election."
It takes voters, and precinct workers. The precinct workers need to verify that the voters actually have the right too vote at that polling place, and that they have not voted at some other place, nor more than once this election at the current polling place. Our goofy laws make it hard for these polling place workers to do theri job. A personal appearance used to be goo enough back in the good old days, or if you live in a small rural town like ai do. These polling place workers know most of the voters on a first name basis and recognize them on sight. P{ity the large city polling place worker. He never saw most of the people he must verify, and the laws make it very hard for him to require these potential voters to prove their right to vote. Likewaise, some of these voters have a hard time proving their right to vote because of this lack of aquantance problem as well.
Marking a ballot and scanning it is the easy part. These ballots also need to be counted, tallied, and reported. This requires honest polling place workers. How to we vet them?
Forget the software problem! Even with software, the identification problem still exists. Someone needed to vet the person who wanted to use the software before the software was ever even installed.