Voting in this country is broken. It is in the interest of corrupt parties that it remains so, but this has been a solved problem for a long time. There will always be chicanery involved in voting, but we can do some easy things to eliminate the problem.
Require a recognized form of ID which ensures citizenry, in order to have the ability to vote
No mail-in ballots aside from soldiers on active-duty and other special cases
Either go back to paper ballots, or require cryptographic proof of unique votes (see Estonia as an example of this)
Regarding the ID system. I have a more formalized propsal you can vote up. The link at the very bottom is for the “Legislative” text of my proposal.