A Formal Framework for Modelling Coercion Resistance and Receipt Freeness

Abstract—Coercion resistance and receipt freeness are criti-cal properties for any voting system. However, many definitions of these properties have been proposed, with varying levels of formality, and there has been little attempt to tie these definitions together or identify relations between them. We give here a general framework for specifying different coercion resistance and receipt freeness properties using the process algebra CSP. The framework is general enough to accommodate a wide range of definitions, including dealing with randomization attacks and forced abstention. We provide models of some simple voting systems, and show how the framework can be used to analyze these models under different definitions of coercion resistance and receipt freeness. Our formalisation highlights the variation between the definitions in the literature. I