Individual Verifiability with Return Codes: Manipulation Detection Efficacy

Researchers advocate for end-to-end verifiable voting schemes to maximise election integrity. At E-Vote-ID 2021, Kulyk et al. proposed to extend the verifiable scheme used in Switzerland (called original scheme) by voting codes to improve it with respect to vote secrecy. While the authors evaluated the general usability of their proposal, they did not evaluate its efficacy with respect to manipulation detection by voters. To close this gap, we conducted a corresponding user study. Furthermore, we study the effect of a video intervention (describing the vote casting process including individual verifiabilty steps) on the manipulation detection rate. We found that 65% of those receiving the video detected the manipulation and informed the support. If we only consider those who stated they (partially) watched the video the rate is 75%. The detection rate for those not having provided the video is 63%. While these rates are significantly higher than the 10% detection rate reported in related work for the original system, we discuss how to further increase the detection rate.