The punchscan voting system

Punchscan was the winning system in the 2006 2007 VoComp competition.

In their own words:

Punchscan is a voting system invented by David Chaum that allows voters to take a piece of the ballot home with them as a receipt. This receipt does not allow voters to prove how they voted to others, but it does permit them to:

  • Verify that they have properly indicated their votes to election officials (cast-as-intended).
  • Verify with extremely high assurance that all votes were counted properly (counted-as-cast).

It uses simple cryptographic techniques to ensure election integrity. The demos on their ‘learn more’ page shows how a voter casts and verifies their vote as well as showing how election integrity can be audited.

After you go through the demos you should also review the excellent FAQ.

The system that is demonstrated can only handle ballots for which there are two candidates for each race. I believe that they have extensions to the system to handle multiple candidates and well as handling

  • alternate voting systems
  • improved support for disabled voters
  • write-in candidates

So it ready for prime-time use?
I don’t know. It has only been used for a few elections and is a very new system so I suspect that it is not ready for wide deployment.

If you are interested in following the development and deployment of punchscan you can join their mailing list.


13 responses to “The punchscan voting system

  1. From:

    A potential objection to this scheme is that the printers (or aggregators) of the top and bottom sheets would be aware of the random permutations and thus could be a colluder in a vote buying scheme.

    Also see Warren Smith’s review of the punchscan system:

  2. Despite what Warren says in his review, I rather liked the flash demos.

  3. There’s some discussion of that issue here:

    Click to access ibs_carback.pdf

    Also, the receipts themselves are Pseudononymous (so long as you don’t put voter name next to each ballot ID they take home), so it’s not as bad of a problem as you might think (on regular opscan, after the election, the Election people are going to have access to the finger prints and other identifying marks on the ballots)…

  4. I do not like how a minimal amount of choices is already built into the system from the get go.

  5. N, I am not sure that I follow your objection. Please clarify if I misinterpret it here.

    I think that you are objecting that each election only allows for two candidates. This is not an actual restriction of their system but rather a simpler case to demonstrate than the multi-candidate case.

    They definately handle the multi candidate case and their photo gallery of images show multicandidate races.

    For example, look at this image from their gallery:

  6. From the abstract of the paper Rick linked to:

    We propose and implement a modification of the Punchscan protocol that simplifies ballot printing and distribution. …each voiter creates a ballot at the polling location by combining independently selected ballot halves, rather than using two pre-selected halves with the same serial number…. This small but nontrivial change lets election officials print and distribute ballots using multiple printers more easily, without giving any one printer the ability to compromise voter privacy with certainty.

  7. N and others — The system supports ranking (this means instant runoff voting and all other variations), plurality (“choose one”), and m out of n (choose 3 of these 5).

    For an example, see the following:

    I think that’s pretty much all the different types of election rules you can run (Range voting can be run by making each candidate their own race, and the scores be the candidates).

    For some of them, the ballot might get a little hard to use/read, but it should be able to run any election type.

  8. Man, if I had’ve heard about Warrens review before, I could’ve hassled him at VoComp :-) As the man who authored the flash presentation, let me say, a picture is worth a thousand words… something that CRV should ponder :-P

  9. Point of order to the moderator, it was VoComp 2007 (i.e. this month)

  10. Pingback: Thank You, Debrah Bowen! « All About Voting

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