So's a lot of stuff. My view is computers are rat bastards that will sell you out in a nanosecond. You should consider everything you do or put on a computer is forever and potentially will be publicly exposed. There is no such thing as completely safe on-line data.
I prefer a system that mails you your ballot, which you then have to fill out and hand in in person at a polling station to be counted on a stand-alone network. Have voting occur over say 3 or 4 days this way to include a weekend or have a national holiday for voting. But, you have to turn it in to a person who verifies who you are using proper ID and it gets counted in front of you.
That isn't absolutely perfect, but it's a damn sight better than unaccountable ballots mailed in or collected by persons unknown.
That's a good idea. Having a week or 10 days to cast your Ballot in person. (how come nobody else thought of that?)