A Proof of Entropy Minimization for Outputs in Deletion Channels via Hidden Word Statistics

From the output produced by a memoryless deletion channel from a uniformly random input of known length $n$, one obtains a posterior distribution on the channel input. The difference between the Shannon entropy of this distribution and that of the uniform prior measures the amount of information about the channel input which is conveyed by the output of length $m$, and it is natural to ask for which outputs this is extremized. This question was posed in a previous work, where it was conjectured on the basis of experimental data that the entropy of the posterior is minimized and maximized by the constant strings $\texttt{000}\ldots$ and $\texttt{111}\ldots$ and the alternating strings $\texttt{0101}\ldots$ and $\texttt{1010}\ldots$ respectively. In the present work we confirm the minimization conjecture in the asymptotic limit using results from hidden word statistics. We show how the analytic-combinatorial methods of Flajolet, Szpankowski and Vall\'ee for dealing with the hidden pattern matching problem can be applied to resolve the case of fixed output length and $n\rightarrow\infty$, by obtaining estimates for the entropy in terms of the moments of the posterior distribution and establishing its minimization via a measure of autocorrelation.Comment: 11 pages, 2 figure

Verification of the Socio-Technical Aspects of Voting: The Case of the Polish Postal Vote 2020

Voting procedures are designed and implemented by people, for people, and with significant human involvement. Thus, one should take into account the human factors in order to comprehensively analyze properties of an election and detect threats. In particular, it is essential to assess how actions and strategies of the involved agents (voters, municipal office employees, mail clerks) can influence the outcome of other agents' actions as well as the overall outcome of the election. In this paper, we present our first attempt to capture those aspects in a formal multi-agent model of the Polish presidential election 2020. The election marked the first time when postal vote was universally available in Poland. Unfortunately, the voting scheme was prepared under time pressure and political pressure, and without the involvement of experts. This might have opened up possibilities for various kinds of ballot fraud, in-house coercion, etc. We propose a preliminary scalable model of the procedure in the form of a Multi-Agent Graph, and formalize selected integrity and security properties by formulas of agent logics. Then, we transform the models and formulas so that they can be input to the state-of-art model checker Uppaal. The first series of experiments demonstrates that verification scales rather badly due to the state-space explosion. However, we show that a recently developed technique of user-friendly model reduction by variable abstraction allows us to verify more complex scenarios

Model Checkers Are Cool: How to Model Check Voting Protocols in Uppaal

The design and implementation of an e-voting system is a challenging task. Formal analysis can be of great help here. In particular, it can lead to a better understanding of how the voting system works, and what requirements on the system are relevant. In this paper, we propose that the state-of-art model checker Uppaal provides a good environment for modelling and preliminary verification of voting protocols. To illustrate this, we present an Uppaal model of Pr\^et \`a Voter, together with some natural extensions. We also show how to verify a variant of receipt-freeness, despite the severe limitations of the property specification language in the model checker

A Survey of Requirements for COVID-19 Mitigation Strategies. Part I: Newspaper Clips

The COVID-19 pandemic has influenced virtually all aspects of our lives. Across the world, countries have applied various mitigation strategies for the epidemic, based on social, political, and technological instruments. We postulate that one should {identify the relevant requirements} before committing to a particular mitigation strategy. One way to achieve it is through an overview of what is considered relevant by the general public, and referred to in the media. To this end, we have collected a number of news clips that mention the possible goals and requirements for a mitigation strategy. The snippets are sorted thematically into several categories, such as health-related goals, social and political impact, civil rights, ethical requirements, and so on. In a forthcoming companion paper, we will present a digest of the requirements, derived from the news clips, and a preliminary take on their formal specification

07311 Abstracts Collection -- Frontiers of Electronic Voting

From July the 29th to August the 3th, 2007, the Dagstuhl Seminar 07311 ``Frontiers of Electronic Voting\u27\u27 was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discussed. Abstracts of the presentations given during the seminar as well as abstracts of seminar results and ideas are put together in this paper. The first section describes the seminar topics and goals in general. Links to extended abstracts or full papers are provided, if available

09311 Abstracts Collection -- Classical and Quantum Information Assurance Foundations and Practice

From 26 July 2009 to 31 July 2009, the Dagstuhl Seminar 09311 ``Classical and Quantum Information Assurance Foundations and Practice\u27\u27 was held in Schloss Dagstuhl~--~Leibniz Center for Informatics. The workshop was intended to explore the latest developments and discuss the open issues in the theory and practice of classical and quantum information assurance. A further goal of the workshop was to bring together practitioners from both the classical and the quantum information assurance communities. To date, with a few exceptions, these two communities seem to have existed largely separately and in a state of mutual ignorance. It is clear however that there is great potential for synergy and cross-fertilization between and this we sought to stimulate and facilitate

Receipt Freeness of Prêt à Voter Provably Secure

Prêt à Voter is an end-to-end verifiable voting scheme that is also receipt free. Formal method analysis was used to prove that Prêt à Voter is receipt free. In this paper we use one of the latest versions of Prêt à Voter[XCH+10] to prove receipt freeness of the scheme using computational methods. We use provable security game models for the first time to prove a paper based voting scheme receipt free. In this paper we propose a game model that defines receipt freeness. We show that in order to simulate the game we require IND-CCA2 encryption scheme to create the ballots. The usual schemes used in constructing Prêt à Voter are either exponential ElGamal or Paillier because of their homomorphic properties that are needed for tallying, however both are IND-CPA secure. We propose a new verifiable shuffle ``D-shuffle\u27\u27 to be used together with an IND-CPA encryption schemes that guarantees that the outputs of the shuffle are IND-CCA2 secure ciphertexts and they are used for constructing the ballots. The idea is based on Naor-Yung transformation[NY95]. We prove that if there exist an adversary that breaks receipt freeness then there exist an adversary that breaks the IND-CCA2 security of Naor-Yung encryption scheme. We further show that the ``D-Shuffle\u27\u27 provides us with the option of having multiple authorities creating the ballots such that no single authority can break voter\u27s privacy