Back in March, I responded to the common argument that since automatic teller machines are widely used and seem to be secure, secure electronic voting must be doable as well. I pointed out a couple of problems with this argument, but I took as a given that ATM machines are in fact, secure. But Matt Blaze recently discovered that ATMs aren't that secure either. When Blaze tried to withdraw cash from a Philadelphia cash machine, he encountered a bunch of problems. The information on the screen was screwed up, the machine gave him $10 more than he'd requested, and the machine failed to give him his receipt. Even more worrisome, when he went into the bank to suggest that they check out the machine and see what might have been wrong with it, the assistant manager actually argued with him, assuring him that the machine was working just fine and Blaze must be imagining things. Incredibly, when he tried to show her a screenshot he had taken with his cell phone, she cut him off by pointing out that photography isn't allowed in the bank.
Obviously, part of the problem here is a bank employee who has a bad attitude. But it also illustrates a couple of additional problems with the "ATMs work so why can't e-voting?" argument. First, people have a habit of trusting machines more than people. When elections are conducted with pencil and paper, everyone understands that some of the human beings might have hidden agendas and need to be watched closely. In contrast, people tend to assume that machines are completely objective and unbiased, and so they're less likely to notice problems with machines even when (as in the case of this bank manager) the evidence is staring them in the face. Second, if it turns out that the ATM screwed up, Blaze will at some point get a statement from his bank telling him how much money the bank thinks he withdrew, and he can object if it differs from what he actually got. There isn't (and due to voter privacy concerns, can't be) a similar process for e-voting. If a paperless voting machine screws up, there's no way to double-check the results after the fact.