Computer security expert Bruce Schneier weighs in on the pros and cons of electronic voting systems, with emphasis on the inherent properties of software that should be taken into account:

Some have argued in favor of touch-screen voting systems, citing the millions of dollars that are handled every day by ATMs and other computerized financial systems. That argument ignores another vital characteristic of voting systems: anonymity. Computerized financial systems get most of their security from audit. If a problem is suspected, auditors can go back through the records of the system and figure out what happened. And if the problem turns out to be real, the transaction can be unwound and fixed. Because elections are anonymous, that kind of security just isn’t possible.

None of this means that we should abandon touch-screen voting; the benefits of DRE machines are too great to throw away. But it does mean that we need to recognize its limitations, and design systems that can be accurate despite them.

Computer security experts are unanimous on what to do. (Some voting experts disagree, but I think we’re all much better off listening to the computer security experts. The problems here are with the computer, not with the fact that the computer is being used in a voting application.) And they have two recommendations:

1. DRE machines must have a voter-verifiable paper audit trails (sometimes called a voter-verified paper ballot). This is a paper ballot printed out by the voting machine, which the voter is allowed to look at and verify. He doesn’t take it home with him. Either he looks at it on the machine behind a glass screen, or he takes the paper and puts it into a ballot box. The point of this is twofold. One, it allows the voter to confirm that his vote was recorded in the manner he intended. And two, it provides the mechanism for a recount if there are problems with the machine.

2. Software used on DRE machines must be open to public scrutiny. This also has two functions. One, it allows any interested party to examine the software and find bugs, which can then be corrected. This public analysis improves security. And two, it increases public confidence in the voting process. If the software is public, no one can insinuate that the voting system has unfairness built into the code. (Companies that make these machines regularly argue that they need to keep their software secret for security reasons. Don’t believe them. In this instance, secrecy has nothing to do with security.)

Computerized systems with these characteristics won’t be perfect -- no piece of software is -- but they’ll be much better than what we have now. We need to start treating voting software like we treat any other high-reliability system. The auditing that is conducted on slot machine software in the U.S. is significantly more meticulous than what is done to voting software. The development process for mission-critical airplane software makes voting software look like a slapdash affair. If we care about the integrity of our elections, this has to change.

Proponents of DREs often point to successful elections as “proof” that the systems work. That completely misses the point. The fear is that errors in the software -- either accidental or deliberately introduced -- can undetectably alter the final tallies. An election without any detected problems is no more a proof the system is reliable and secure than a night that no one broke into your house is proof that your door locks work. Maybe no one tried, or maybe someone tried and succeeded...and you don’t know it.  [full essay]

(Via makinglight.)