April 23, 2014

avatar

Unpeeling the mystique of tamper-indicating seals

As computer scientists have studied the trustworthiness of different voting technologies over the past decade, we notice that “security seals” are often used by election officials. It’s natural to wonder whether they really provide any real security, or whether they are just for show. When Professor Avi Rubin volunteered as an election judge (Marylandese for pollworker) in 2006, one of his observations that I found most striking was this:


Avi Rubin


“For example, I carefully studied the tamper tape that is used to guard the memory cards. In light of Hursti’s report, the security of the memory cards is critical. Well, I am 100% convinced that if the tamper tape had been peeled off and put back on, nobody except a very well trained professional would notice it. The tamper tape has a tiny version of the word “void” appear inside it after it has been removed and replaced, but it is very subtle. In fact, a couple of times, due to issues we had with the machines, the chief judge removed the tamper tape and then put it back. One time, it was to reboot a machine that was hanging when a voter was trying to vote. I looked at the tamper tape that was replaced and couldn’t tell the difference, and then it occurred to me that instead of rebooting, someone could mess with the memory card and replace the tape, and we wouldn’t have noticed. I asked if I could play with the tamper tape a bit, and they let me handle it. I believe I can now, with great effort and concentration, tell the difference between one that has been peeled off and one that has not. But, I did not see the judges using that kind of care every time they opened and closed them. As far as I’m concerned, the tamper tape does very little in the way of actual security, and that will be the case as long as it is used by lay poll workers, as opposed to CIA
agents.”

Avi is a first-rate expert in the field of computer security, in part because he’s a good experimentalist—as in, “I asked if I could play with the tamper tape.” To the nonexpert,
security seals have a mystique: there’s this device there, perhaps a special tape or perhaps a thing that looks like a little blue plastic padlock. Most of us encounter these devices in a context where we can’t “play with” them, because that would be breaking the rules: on voting machines, on our electric meter, or whatever. Since we don’t play with them, we can’t tell whether they are secure, and the mystique endures. As soon
as Avi played with one, he discovered that it’s not all that secure.

In fact, we have a word for a piece of tape that only gives the appearance of working:

band-aid: (2) a temporary way of dealing with a problem that will not really solve it (Macmillan Dictionary)

In the last couple of years I’ve been studying security seals on voting machines in New Jersey. For many decades New Jersey law has required that each voting machine be “sealed with a numbered seal”, just after it is prepared for each election (NJSA 19:48-6). Unfortunately it’s hard for legislators to write into the statutes exactly how well these seals must work. Are tamper-indicating seals used in elections really secure? I’ll address that question in my next few articles.