Assuring the Integrity of Voting Using Cryptography

American voters have no way of knowing that our votes have been counted, or counted correctly.

We go to the polls and we punch buttons on a screen or fill out paper ballots and put them in a box, but we don’t know if the electronic voting machine works correctly, if the ballot box made it to the election office, or if the ballots have been accurately tallied. The rise of electronic voting machines with secret, proprietary software has only made these problems worse.

On Monday, laureate Ron Rivest, one of the inventors of the RSA cryptography algorithm that underlies most secure internet transactions, described the work he and others have done to use cryptography to solve these problems.

The starting place for his work is simple, though not an acceptable solution in itself: Imagine that when a vote was recorded, it was registered on a website for everyone to see. Then voters could go home, check the website, and know that their vote was accurately recorded. Furthermore, since all the data would be publicly available, anyone interested could count up the results and check the election officials’ work.

The problem with this is that people often don’t want other people to be able to see whom they voted for. Furthermore, such a system would raise the prospect of vote selling, since anyone could prove whom they voted for (even now, that’s a problem with voting by mail, and that’s one of the central reasons that Rivest strongly opposes the idea of internet voting).

So in Rivest’s plan, when a voter is given a record of his vote, it’s encrypted. If the voter wants, he can have the machine decrypt it on the spot to check it and then re-encrypt it, assuring himself of its accuracy. He can then take the encrypted version home and check that it’s been recorded — though at home, he can’t decrypt it to see whom he voted for, and hence can’t prove to anyone else whom he voted for.

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