Tuesday, November 3, 2009

Scantegrity: E-voting System Lets Voters Verify Their Ballots are Counted

Via ComputerWorld -

A new electronic voting system being used today for the first time in a government election in the U.S. will allow voters and elections auditors in Takoma Park, Md. to go online and verify whether votes have been correctly recorded.

The voting system is called Scantegrity and was developed by independent cryptographer David Chaum, along with researchers from the University of Maryland-Baltimore, the George Washington University, MIT, the University of Ottawa and the University of Waterloo. It uses cryptographic techniques to let both voters and election auditors check whether votes have been cast and counted accurately.

The Scantegrity technology is being used to augment regular optical-scan voting systems in Takoma Park's city council election. To cast a vote, an individual takes a paper ballot and fills in the optical-scan oval next to the name of the selected candidate using a pen with a special type of ink. When the bubble is filled, it reveals a three-digit confirmation number already printed on the ballot using an invisible marker.

That three-digit code is a sort of randomly generated cryptographic marker that's used to associate the voter's choice with the appropriate candidate. The codes are separately randomized for each oval and for each ballot, ensuring that the codes don't reveal who an individual voted for, Chaum said in an interview with Computerworld.

Voters can use that confirmation code to later log into the city's election Web site to confirm that their votes were recorded accurately. If the code is present on the Web site, it means the ballot was counted correctly, he said.

Scantegrity also lets election auditors -- and even third-party observers -- check whether the results were accurately tabulated without revealing how each individual vote was cast, Chaum said. Though it is not possible to link an individual ballot to a specific candidate, auditors can verify that the codes do lead to the recorded votes.

Scantegrity uses cryptographic techniques to first map each code to the associated candidate and then completely conceals the link. It then uses a concept known as "zero-knowledge proof" to show auditors that the codes do in fact correspond to the right candidates, said Aleks Essex, a PhD. student in computer science at the University of Ottawa who was involved in the Scantegrity effort.



Scantegrity is an open source election verification technology for optical scan voting systems. It uses privacy preserving confirmation numbers to allow each voter to verify her vote is counted. The confirmation numbers also allow anyone to verify that all the votes were counted correctly.

Election officials can use Scantegrity as a standalone system or as an add-on to provide a low-footprint audit companion solution for any current optical scan voting system. All extra functionality is optional for voters, staying out of the way of what voters need to do—vote.

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