Build a better voting machine

August 17, 2007

Two security experts described some ways to improve voting machines. In designing a secure voting machine, the central assumption should be that the machines will be hacked. Therefore, it’s foolish to rely on one machine from one company. Instead, as these guys describe, one machine should generate a machine-readable paper record of the vote that can be verified by the voter and scanned in by another machine. A voting site might have a dozen voting machines and 1 optical scanner. It’s still possible to hack the optical scanner to manipulate votes. So I propose that each voting machine map the candidate names to a set of random numbers: (Machine1 Bush 8204). Every machine is different. After voting, the receipt will say you voted for Bush, but the optical scanner will read in the number 8204 (and 2947 from machine 2, 1695 from machine 3, etc.). The scanner tabulates the number of votes for 8204, but it has no idea what that means. Therefore, a hacker wouldn’t be able to manipulate votes because he doesn’t know what these numbers represent. The scanner sends these random numbers to the central computer. Again, the central computer has no idea what these numbers represent. Finally, the voting machines send their mappings and votes to another central computer. Now the central computers can map (8204 -> Bush) to determine the final tally and verify it against each voting machines records. The central computer can send a report back to each voting station for poll workers to manually verify the total against the voting machines’ numbers.

How can a hacker defeat this system? If he hacks the optical scanner or the first central computer, he’ll only see a bunch of meaningless random numbers. If he hacks the second central computer (the one that gets the mappings and votes), he can’t do anything because the results must match the first central computer. If he hacks both central computers, he still can’t do much because the numbers will be double-checked against the voting machines. If he hacks all the voting machines, he could assign Bush’s number to Gore; therefore, the voter see “Gore” on his paper ballot, but optical scanner reads Bush’s number. However, the poll workers can spot check the numbers to ensure they are different. This seems like a decent solution, though it’s rather complicated. It needs to be simplified because poll workers are fairly dumb. You can’t rely on them to do anything right, especially when there are several independent steps. Nevertheless, I don’t think it’s difficult to build a secure electronic voting system. It would certainly be different from the one we’ve got today.

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