Prêt à Voter providing everlasting privacy

This paper shows how Prêt à Voter can be adjusted in order to provide everlasting privacy. This is achieved by adapting the ballot generation and anonymisation process, such that only unconditional hiding commitments and zero knowledge proofs are published for verification, thus ensuring privacy towards the public. This paper presents a security analysis carried out in a collaboration between computer scientists and legal researchers. On the technical side it is shown that the modified Prêt à Voter provides verifiability, robustness, and everlasting privacy towards the public. Everlasting privacy towards the authorities can be achieved by implementing several organisational measures. A legal evaluation of these measures demonstrates that the level of privacy achieved would be acceptable under German law.