On the privacy threats of electronic poll books

Electronic poll books can rapidly check the eligibility of a voter due to their ability to quickly search lists. However, they also introduce a factor of concern: if the electronic poll book records the order of sign-ins and the voting machine or optical scanner records the order in which the voters cast their ballots, ballot secrecy can be compromised. Worse, if the time at which each voter signs-in and the time at which each ballot is cast are recorded, ballot secrecy is lost. It is surprisingly difficult to avoid saving such timing information, for example in event logs, and even more difficult to verify that no such information is saved. In addition, due to operational complexities, even the more efficient electronic poll books can act as a bottleneck in the voting process. We propose a simple technique to address these concerns, by allowing voters to sign-in from home, and print out a bar-coded ticket to be presented at the check-in table. Using blind signatures, this ticket need not reveal information on the voter´s identity to the check-in table at the precinct. The ticket proves than the voter is authorized to vote on a particular ballot style without disclosing her identity.