This is a solved problem, but for reasons I don't understand it has only been used in a few elections. Do this: • Use paper ballots that are marked by the vote

This is a solved problem, but for reasons I don't understand it has only been used in a few elections. Do this: • Use paper ballots that are marked by the voter filling in ovals next to the name of the candidate or proposition they are voting for using a marker supplied by the election officials. • These paper ballots can be hand counted or counted by simple optical scan machines that are already widely in use in many places. • By using some clever chemistry in the ink when you print the ballots and in the marker used to mark it you can print a code in each of the ovals that is invisible until the oval is filled in using that special marker. By using some clever cryptographic techniques to come up with those invisible codes you can make a system with the following properties. 1. After the election all of the cast ballots can be published, allowing anyone to do an independent recount. 2. Any individual voter after the election can, if they noted the code that was on their ballot for a particular candidate, verify that their particular ballot was included in the count and that their vote counted toward the correct candidate. 3. An individual cannot prove to a third party that they voted for a particular candidate. Here is a paper on such a system: https://eprint.iacr.org/2010/502.pdf https://eprint.iacr.org/2010/502.pdf Wikipedia article on it: https://en.wikipedia.org/wiki/Scantegrity https://en.wikipedia.org/wiki/Scantegrity Here is a paper showing how it satisfies item #3: https://eprint.iacr.org/2010/502 https://eprint.iacr.org/2010/502