Automated Verification of Remote Electronic Voting Protocols in the Applied Pi-Calculus

Abstract

We present a general technique for modeling remote electronic voting protocols in the applied pi-calculus and for automatically verifying their security. In the first part of this paper, we provide novel definitions that address several important security properties. In particular, we propose a new formalization of coercion-resistance in terms of observational equivalence. In contrast to previous definitions in the symbolic model, our definition of coercion-resistance is suitable for automation and captures simulation and forcedabstention attacks. Additionally, we express inalterability, eligibility, and non-reusability as a correspondence property on traces. In the second part, we use ProVerif to illustrate the feasibility of our technique by providing the first automated security proof of the coercion-resistant protocol proposed by Juels, Catalano, and Jakobsson.21st IEEE Computer Security Foundations Symposium 978-0-7695-3182-3/08 $25.00

Defining Privacy for Weighted Votes, Single and Multi-voter Coercion

“…A protocol satisfies Swap-Coercion-Resistance (SwCR) if for any context S corresponding to a voting process with a hole for two voters and for all votes σ v A and σ v B there exists a process V such that for any context C with C = νc 1 …”

“…Related Work: Previous research on formal verification of voting protocols concerned privacy properties (privacy, receipt-freeness and coercion-resistance) [1][2][3][4][5][6][7][8], election verifiability [9,10], or both [11][12][13].…”

Automated Anonymity Verification of the ThreeBallot Voting System

“…Some other voting systems have been at least partially verified automatically against privacy-related properties (for example, Civitas [3] in [8] with handproofs, FOO [2] in [9] with a compiler, and Prêtà Voter [10] in [11]); but the ThreeBallot voting system has not yet been subjected to automated formal verification.…”

Towards Automatic Analysis of Election Verifiability Properties

“…We work in the applied pi calculus [2], and we use the ProVerif software tool [8] to automate verification. (The calculus and the tool have already been successful in analysing other properties of electronic voting systems [14,4].) Our approach puts significant emphasis on the automatic analysis of the verifiability property, using ProVerif.…”

“…This distinction is made for compatibility with protocols which do not offer eligibility verifiability.) These three aspects of verifiability are related to the following correctness properties [4], defined with respect to honest protocol executions:…”