There's to my knowledge no digital voting system used in practice that wasn't found to be severely lacking in terms of security. The famous Estonian iVote syste

There's to my knowledge no digital voting system used in practice that wasn't found to be severely lacking in terms of security. The famous Estonian iVote system is a case in point; it wouldn't be infeasible for a large, dedicated actor (e.g. Russia) to manipulate it, or at least to cast severe doubt upon its results. Mainly that's because it's really hard to simultaneously maintain both anonymity and integrity, both of which are essential to voting. Lest you think anonymity is not important, think about what happens if I can see how you voted: I could simply pay you for voting "the right way". The research literature is full with proposed electronic voting schemes, and security reviews thereof. As far as I can see, current mainstream consensus in the security community is that there is no system secure enough to be recommended, and many doubt that it can ever be done.