On Trade-offs of Applying Block Chains for Electronic Voting Bulletin Boards Sven Heiberg1, Ivo Kubjas1, Janno Siim3;4, and Jan Willemson2;3 1 Smartmatic-Cybernetica Centre of Excellence for Internet Voting Ulikooli¨ 2, 51003 Tartu, Estonia fsven,
[email protected] 2 Cybernetica AS, Ulikooli¨ 2, 51003 Tartu, Estonia
[email protected] 3 Software Technology and Applications Competence Center Ulikooli¨ 2, 51003 Tartu, Estonia 4 Institute of Computer Science, University of Tartu Ulikooli¨ 18, 50090 Tartu, Estonia
[email protected] Abstract. This paper takes a critical look at the recent trend of building electronic voting systems on top of block chain technology. Even though being very appealing from the election integrity perspective, block chains have numerous technical, economical and even political drawbacks that need to be taken into account. Selecting a good trade-off between de- sirable properties and restrictions imposed by different block chain im- plementations is a highly non-trivial task. This paper aims at bringing some clarity into performing this task. We will mostly be concentrating on public permissionless block chains and their applications as bulletin board implementations as these are the favourite choices in majority of the recent block chain based voting protocol proposals. 1 Introduction In virtually all of the modern democratic societies, democracy (translated from Greek roughly as rule of the people) is implemented via some sort of public opinion polling e.g. voting on the elections of representative bodies. Regrettably, the process of public polling is very fragile. Many things can go wrong, and have gone wrong in the history of elections. To address the his- torically experienced problems, many requirements have been put forward and many measures have been developed to meet them.