Auditing for privacy in threshold PKE e-voting

Abstract

Purpose

This paper aims to investigate the importance of auditing for election privacy via issues that appear in the state-of-the-art implementations of e-voting systems that apply threshold public key encryption (TPKE) in the client such as Helios and use a bulletin board (BB).

Design/methodology/approach

Argumentation builds upon a formal description of a typical TPKE-based e-voting system where the election authority (EA) is the central node in a star network topology. The paper points out the weaknesses of the said topology with respect to privacy and analyzes how these weaknesses affect the security of several instances of TPKE-based e-voting systems. Overall, it studies the importance of auditing from a privacy aspect.

Findings

The paper shows that without public key infrastructure (PKI) support or – more generally – authenticated BB “append” operations, TPKE-based e-voting systems are vulnerable to attacks where the malicious EA can act as a man-in-the-middle between the election trustees and the voters; hence, it can learn how the voters have voted. As a countermeasure for such attacks, this work suggests compulsory trustee auditing. Furthermore, it analyzes how lack of cryptographic proof verification affects the level of privacy that can be provably guaranteed in a typical TPKE e-voting system.

Originality/value

As opposed to the extensively studied importance of auditing to ensure election integrity, the necessity of auditing to protect privacy in an e-voting system has been mostly overlooked. This paper reveals design weaknesses present in noticeable TPKE-based e-voting systems that can lead to a total breach of voters’ privacy and shows how auditing can be applied for providing strong provable privacy guarantees.

Citation

Kiayias, A., Zacharias, T. and Zhang, B. (2017), "Auditing for privacy in threshold PKE e-voting", Information and Computer Security, Vol. 25 No. 1, pp. 100-116. https://doi.org/10.1108/ICS-07-2016-0056