Tuesday is Election Day here in the United States, with hundreds of seats in Congress and thousands of local offices up for grabs.
Tens of millions of voters will be using electronic voting machines to record their ballot. The new technology is not without controversy.
After the 2000 presidential election and the difficulties counting punch card ballots, Congress passed the Help America Vote Act, which provided billions of dollars to local election boards to buy new electronic voting machines to replace antiquated models.
The new machines look a bit like laptop computers, usually with a touch-screen rather than a keyboard.
They're seen to have numerous advantages. For example, they can be programmed so voters won't risk losing their ballots by voting for two candidates for one office.
They can also help handicapped voters - especially the blind - who can use headphones and a synthesized voice to guide them through the process without assistance. Voters who can see, but not all that well, can also benefit from the new technology, as voting machine maker Diebold demonstrates in a promotional video that explains that "you can magnify or change the contrast of your ballot to help increase readability.
The machines also allow voters to display ballots in other languages.
But critics have emerged who challenge the security of electronic voting. Among the most prominent is Avi Rubin, a computer science professor at Johns Hopkins University and author of a new book on the subject, .
While paper ballots and earlier voting technologies have always been subject to manipulation, the problem with computerized voting, he says, is that a software flaw - whether inadvertent or deliberate - can result in massive irregularities.
"The software for these electronic voting machines is kept proprietary, and furthermore the risks of wholesale fraud with the electronic machines is much greater because the same software runs on tens of thousands of machines, and if there's a bug in it, that gets replicated," said Rubin, who was among those who studied Diebold voting machine software that became public several years ago. In an interview, he said it was full of what he called "amateurish mistakes."
"In particular, the way that they used cryptography was using outdated ciphers. And in some places where they needed to use cryptography, it wasn't used at all. And we came up with some scenarios, for example, where instead of taking the smart card that is used to control how many times people vote -- namely making sure they can only vote once -- and how you could vote multiple times with a smart card that you might bring from home."
Diebold has disputed these and other technical criticisms and says, in any event, the source code Rubin and others examined was incomplete and not used on voting machines in actual elections.
But possible design flaws in the software are not the only issue. There is the risk that electronic voting machines - which are really specialized computers - could become infected by a virus.
Computer Science Professor Edward Felton of Princeton University demonstrated to members of Congress how a computer virus could compromise electronic voting. Felton used the popular Diebold AccuVote-TS model in an imaginary election contest between George Washington and Benedict Arnold. He cast three ballots for Washington and then retrieved the results as recorded by the virus-infected machine.
"In this machine the records were modified by our virus," Felton told the lawmakers. "And it shows George Washington with one vote and Benedict Arnold with two. Every record in the machine and outside the machine is consistent with this fraudulent result."
In other words, the virus switched two of the three votes to the other candidate, with no apparent evidence that there was anything wrong.
The answer to possible electronic shenanigans is an old but seemingly reliable technology: paper.
Avi Rubin's solution is to use the electronic machines as what he ironically calls a "$5,000 pencil" to print out a paper ballot, which would then be counted by an electronic scanner. The paper is retained in case a recount is needed.
But Michael Shamos, a computer science professor at Carnegie Mellon University, says the reliance on paper ballots -- even if counted by a state-of-the-art scanner -- subjects voting to the risks of fraud that modern technology was supposed to eliminate.
"Paper ballots that are scanned electronically are certainly subject to the same kinds of tampering - in fact it's easier, in general, to tamper with those because they are cut sheets of paper. They're individual pieces of paper. There are all sorts of problems with optical scan voting, but it's in widespread use around the country," Shamos said.
Still, many voters say they are more comfortable if there is some kind of paper evidence of their vote, what election officials call a voter verified paper audit trail, or VPAT.
But that VPAT can itself be a problem. In Cleveland, Ohio, where voting machines produce a paper tally, election official Keith Cunningham says there were numerous discrepancies.
"Over and over and over we encountered tapes that were missing, that were in some way compromised," he said. "Nearly 17 percent of those tapes showed a vote discrepancy of one to five votes from the electronic machine. And nearly 10 percent of those tapes were either destroyed, blank, missing, or in some other way, compromised."
In 2004, almost 30 percent of American voters cast their ballot on computerized voting machines. This year, the number is expected to be more than 40 percent.