[specialist]

Good question. Volunteer to help with your local elections. Learn how it's done.

As for blockchains: Voters sign in before they cast their ballot. If the order in the pollbook matches the order the ballots are recorded, no more secret ballot.

Any crypto- blocko- based system that both protects the secret ballot and ensures the public vote count (aka Australian Ballot) has to create a digital equivalent to the physical secure one-way hash (shuffle) of dropping a ballot into a box.