E-Voting News and Analysis, from the Experts

Wednesday November 03, 2004

Phonecams and the Secret Ballot

Filed under: — Felten @ 9:20 am UTC

Secrecy of the ballot is one of the most important security requirements for elections. Voters must be able to keep their votes secret. But that is only half of the secret ballot requirement. The other half, which is sometimes overlooked, is that a voter should not be able to prove to a third party how he voted, even if the voter wants to do so.

Allowing voters to prove how they voted opens the door to vote-buying and coercion. It’s much harder to buy a vote if the buyer can’t be sure that he is really getting what he paid for; and it’s harder to strongarm someone into voting your way if you they can undetectably vote for their own candidate. For example, if you can prove how you voted, then the boss or the union chief can tell you not to bother showing up for work the next day without proof that you voted for a certain candidate.

Most voting systems are designed to prevent voters from proving how they voted. But new recording technology allows voters to record their votes on video, using cellphone cameras or similar small devices. Alex Halderman decided to demonstrate this by recording his own vote yesterday. Alex writes:

[Yesterday] I voted for John Kerry–and I can prove it, thanks to my Nokia 6230 camera phone:


You see, my phone can record short video clips as well as still photos. Inside the election booth, I shot a clip showing my choice of candidate, my face (so you know it’s me voting), and the final lever pull that locked in the vote (so you know I didn’t change it after turning off the camera).

[I posted this at Alex’s request.]


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  1. I don’t know about that. I’ve done some video editing, and I’m pretty sure that you could use this technique to sell your vote to both parties and do some video editing to produce the right clip for each one.

    Comment by Avi Rubin — Wednesday November 03, 2004 @ 1:07 pm UTC

  2. Avi,

    I think a clever adversary could prevent video editing by insisting that the voter send the video directly from his mobile phone (which lacks editing capability) immediately upon recording it. Any video snippet that comes by email,immediately and direct from the phone, is like to be unedited.

    Comment by Ed Felten — Wednesday November 03, 2004 @ 2:50 pm UTC

  3. Couldn’t a voter who wanted to prove to a third party how he voted use an absentee ballot to do so?

    Comment by Andrew Tappert — Wednesday November 03, 2004 @ 4:13 pm UTC

  4. Andrew,
    Not necessarily. In some states anyone can get an absentee ballot, just by asking. In other states, absentee ballots are given only for certain specified reasons, and only then with some kind of documentation. In states of the second type, absentee ballot problems of the type you describe are less likely.

    Comment by Ed Felten — Wednesday November 03, 2004 @ 4:35 pm UTC

  5. I don’t know, Ed. On my cell phone, I can store a video that’s been edited on my SD card and then send it. What I don’t know for sure is if I can make it look like a video I just took. But, I’m sure that such an application could be developed for the Treo. The application would take a preloaded and edited video and send it through the phone’s email system as if it were just taken. That can’t be too hard to do.

    Comment by Avi Rubin — Thursday November 04, 2004 @ 1:06 pm UTC

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