Go to paper ballots. Keep them after the election in case of a recount. Get rid of voting machines which are nothing more than desktop computers running a ballot program. And could be hacked at the factory, at the polls, over the net, every which way, and you could never figure out what happened.
Let's have some security on voter registration lists. If hostile hackers managed to erase say 10% of all Republicans registered, that would throw the election to the Democrats. A voter shows up at the polls, and he isn't on the registration list, he doesn't get to vote. Ten percent of either side is enough to decide most elections.
Since we cannot do any paperwork without putting it on computer these days, we need some security on the machines that hold the voter registration lists at cities and towns. The machine[s] that store and modify the voter registration lists must NOT be connected to the public internet in any way shape or fashion. Keep the machines in a locked room and only allow a minimum of people access to them. Backup the voter registration list[s] every week or so, and store the backups off line and off site. When new voters are registered give them a printed certificate of registration that they can use to prove they registered should the computers mess up some how.