{"type":"ScholarlyArticle","title":"Protecting Elections by Recounting Ballots","authors":[{"name":"Edith Elkind","slug":"edith-elkind","given":"Edith","family":"Elkind","affiliation":"Department of Computer Science , University of Oxford"},{"name":"Jiarui Gan","slug":"jiarui-gan","given":"Jiarui","family":"Gan","affiliation":"Department of Computer Science , University of Oxford"},{"name":"Svetlana Obraztsova","slug":"svetlana-obraztsova","given":"Svetlana","family":"Obraztsova","affiliation":"School of Computer Science and Engineering , Nanyang Technological University"},{"name":"Zinovi Rabinovich","slug":"zinovi-rabinovich","given":"Zinovi","family":"Rabinovich","affiliation":"School of Computer Science and Engineering , Nanyang Technological University"},{"name":"Alexandros A. Voudouris","slug":"alexandros-a-voudouris","given":"Alexandros A.","family":"Voudouris","affiliation":"Department of Computer Science , University of Oxford"}],"abstract":"Complexity of voting manipulation is a prominent topic in computational social choice. In this work, we consider a two-stage voting manipulation scenario. First, a malicious party (an attacker) attempts to manipulate the election outcome in favor of a preferred candidate by changing the vote counts in some of the voting districts. Afterwards, another party (a defender), which cares about the voters' wishes, demands a recount in a subset of the manipulated districts, restoring their vote counts\r\nto their original values. We investigate the resulting Stackelberg game for the case where votes are aggregated using two variants of the Plurality rule, and obtain an almost complete picture of the complexity landscape, both from the attacker's and from the defender's perspective.","doi":"10.24963/ijcai.2019/37","url":"https://ijcai.org/proceedings/2019/37","pdf":"https://ijcai.org/proceedings/2019/0037.pdf","markdown":"https://ijcai.org/proceedings/2019/37.md","bibtex":"https://ijcai.org/proceedings/2019/bibtex/37","volume":{"slug":"2019","title":"Proceedings of the Twenty-Eighth International Joint Conference on Artificial Intelligence","short_title":"IJCAI 2019","url":"https://ijcai.org/proceedings/2019/","year":2019,"location":"Macao","dates":"10-16 August 2019","editors":"Sarit Kraus","isbn":"978-0-9992411-4-1","publisher":"International Joint Conferences on Artificial Intelligence Organization","doi_prefix":"10.24963/ijcai.2019"},"section":"Agent-based and Multi-agent Systems","track":"Main track","number":37,"pages":{"first":259,"last":265},"keywords":["Agent-based and Multi-agent Systems: Algorithmic Game Theory","Agent-based and Multi-agent Systems: Computational Social Choice","Agent-based and Multi-agent Systems: Voting"],"videos":[],"references":[{"position":1,"raw":"[Bredereck et al., 2016] Robert Bredereck, Piotr Fal- iszewski, Rolf Niedermeier, and Nimrod Talmon. 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