Combinatorial Solutions Providing Improved Security for the Generalized Russian Cards Problem

We present the first formal mathematical presentation of the generalized Russian cards problem, and provide rigorous security definitions that capture both basic and extended versions of weak and perfect security notions. In the generalized Russian cards problem, three players, Alice, Bob, and Cathy, are dealt a deck of $n$ cards, each given $a$, $b$, and $c$ cards, respectively. The goal is for Alice and Bob to learn each other's hands via public communication, without Cathy learning the fate of any particular card. The basic idea is that Alice announces a set of possible hands she might hold, and Bob, using knowledge of his own hand, should be able to learn Alice's cards from this announcement, but Cathy should not. Using a combinatorial approach, we are able to give a nice characterization of informative strategies (i.e., strategies allowing Bob to learn Alice's hand), having optimal communication complexity, namely the set of possible hands Alice announces must be equivalent to a large set of $t-(n, a, 1)$-designs, where $t=a-c$. We also provide some interesting necessary conditions for certain types of deals to be simultaneously informative and secure. That is, for deals satisfying $c = a-d$ for some $d \geq 2$, where $b \geq d-1$ and the strategy is assumed to satisfy a strong version of security (namely perfect $(d-1)$-security), we show that $a = d+1$ and hence $c=1$. We also give a precise characterization of informative and perfectly $(d-1)$-secure deals of the form $(d+1, b, 1)$ satisfying $b \geq d-1$ involving $d-(n, d+1, 1)$-designs

Extended Combinatorial Constructions for Peer-to-peer User-Private Information Retrieval

We consider user-private information retrieval (UPIR), an interesting alternative to private information retrieval (PIR) introduced by Domingo-Ferrer et al. In UPIR, the database knows which records have been retrieved, but does not know the identity of the query issuer. The goal of UPIR is to disguise user profiles from the database. Domingo-Ferrer et al.\ focus on using a peer-to-peer community to construct a UPIR scheme, which we term P2P UPIR. In this paper, we establish a strengthened model for P2P UPIR and clarify the privacy goals of such schemes using standard terminology from the field of privacy research. In particular, we argue that any solution providing privacy against the database should attempt to minimize any corresponding loss of privacy against other users. We give an analysis of existing schemes, including a new attack by the database. Finally, we introduce and analyze two new protocols. Whereas previous work focuses on a special type of combinatorial design known as a configuration, our protocols make use of more general designs. This allows for flexibility in protocol set-up, allowing for a choice between having a dynamic scheme (in which users are permitted to enter and leave the system), or providing increased privacy against other users.Comment: Updated version, which reflects reviewer comments and includes expanded explanations throughout. Paper is accepted for publication by Advances in Mathematics of Communication

A classical reactive potential for molecular clusters of sulphuric acid and water

We present a two-state empirical valence bond (EVB) potential describing interactions between sulphuric acid and water molecules and designed to model proton transfer between them within a classical dynamical framework. The potential has been developed in order to study the properties of molecular clusters of these species, which are thought to be relevant to atmospheric aerosol nucleation. The particle swarm optimisation method has been used to fit the parameters of the EVB model to density functional theory (DFT) calculations. Features of the parametrised model and DFT data are compared and found to be in satisfactory agreement. In particular, it is found that a single sulphuric acid molecule will donate a proton when clustered with four water molecules at 300 K and that this threshold is temperature dependent

Humoral response to Type-A derived genetically modified live attenuated Francisella tularensis in rabbits

Francisella tularensis is a gram negative, non-motile, coccobacillus that is the causative agent of tularemia. There is concern that F. tularensis could be used as a biological weapon and development of vaccines is a high priority. Type A strains are highly virulent but the current live vaccine strain (LVS) is based on a type B strain which is only partially protective against aerosol challenge with SCHU S4 (S4), a type A strain. Historically mice have been the most commonly used model to study vaccines and pathogenesis of F. tularensis. However, mice are acutely sensitive to tularemia such that strains that are attenuated or avirulent in other mammals cause lethal disease in mice. Therefore, the rabbit model has been used in these studies because New Zealand White rabbits have a disease course and susceptibility similar to humans. The data presented here will demonstrate that the humoral immune response plays a role in the protection and survival from a F. tularensis infection. A novel ELISA assay has been used to examine antibody titers against F. tularensis in the plasma of rabbits post vaccination and analyzed to determine if there is a correlation to survival against challenge with SCHU S4. In addition, data was analyzed to compare various vaccines, vaccination routes, and vaccine doses to determine if one provided better protection and higher survival rate

Research Brief One-Sheet No.8: The Impact of Police Crime on LGBTQ+ People

This research brief provides a summary of a research presentation at the Forum on 21st Century Policing: Protecting the Rights of LGBTQ+ People held by the Office of Community Oriented Policing Services at the U.S. Department of Justice, on July 21, 2016, in Washington, DC