The economics of split-ticket voting in representative democracies

In U.S. elections, voters often vote for candidates from different parties for president and Congress. Voters also express dissatisfaction with the performance of Congress as a whole and satisfaction with their own representative. We develop a model of split-ticket voting in which government spending is financed by uniform taxes but the benefits from this spending are concentrated. While the model generates split-ticket voting, overall spending is too high only if the president’s powers are limited. Overall spending is too high in a parliamentary system, and our model can be used as the basis of an argument for term limits.Government spending policy

The emergence of local elite networks: Structure or preference? - An econometric approach -

This paper analyzes the determinants and causes of communication in local elite networks. The database comprises four rural county elite networks from Poland and Slovakia. Socio spatial processes allowing a flexible incorporation of individual specific information are embedded within a logit framework. Empirical analysis focuses on the assessment of the hypotheses, whether preferences measured by socio demographic factors and political ideology or institutional settings (structure) influence individual communication in local elite networks. The results suggest that while in high performing communities institutional settings, i.e. a common membership in local organizations, are the most important factors determining communication, in low performing communities communication ties are stronger determined by actors’ preferences, i.e. ideological distances and socio demographic factors. Moreover, communication is more centralized for the latter when compared to the former socio spatial process

Efficient Asynchronous Byzantine Agreement without Private Setups

Efficient asynchronous Byzantine agreement (BA) protocols were mostly studied with private setups, e.g., pre-setup threshold cryptosystem. Challenges remain to reduce the large communication in the absence of such setups. Recently, Abraham et al. (PODC'21) presented the first asynchronous validated BA (VBA) with expected $O(n^3)$ messages and $O(1)$ rounds, relying on only public key infrastructure (PKI) setup, but the design still costs $O({\lambda}n^3 \log n)$ bits. Here $n$ is the number of parties, and $\lambda$ is a cryptographic security parameter. In this paper, we reduce the communication of private-setup free asynchronous BA to expected $O(\lambda n^3)$ bits. At the core of our design, we give a systematic treatment of common randomness protocols in the asynchronous network, and proceed as: - We give an efficient reasonably fair common coin protocol in the asynchronous setting with only PKI setup. It costs only $O(\lambda n^3)$ bits and $O(1)$ rounds, and ensures that with at least 1/3 probability, all honest parties can output a common bit that is as if randomly flipped. This directly renders more efficient private-setup free asynchronous binary agreement (ABA) with expected $O(\lambda n^3)$ bits and $O(1)$ rounds. - Then, we lift our common coin to attain perfect agreement by using a single ABA. This gives us a reasonably fair random leader election protocol with expected $O(\lambda n^3)$ communication and expected constant rounds. It is pluggable in all existing VBA protocols (e.g., Cachin et al., CRYPTO'01; Abraham et al., PODC'19; Lu et al., PODC'20) to remove the needed private setup or distributed key generation (DKG). As such, the communication of private-setup free VBA is reduced to expected $O(\lambda n^3)$ bits while preserving fast termination in expected $O(1)$ rounds

Hierarchical Group and Attribute-Based Access Control: Incorporating Hierarchical Groups and Delegation into Attribute-Based Access Control

Attribute-Based Access Control (ABAC) is a promising alternative to traditional models of access control (i.e. Discretionary Access Control (DAC), Mandatory Access Control (MAC) and Role-Based Access control (RBAC)) that has drawn attention in both recent academic literature and industry application. However, formalization of a foundational model of ABAC and large-scale adoption is still in its infancy. The relatively recent popularity of ABAC still leaves a number of problems unexplored. Issues like delegation, administration, auditability, scalability, hierarchical representations, etc. have been largely ignored or left to future work. This thesis seeks to aid in the adoption of ABAC by filling in several of these gaps. The core contribution of this work is the Hierarchical Group and Attribute-Based Access Control (HGABAC) model, a novel formal model of ABAC which introduces the concept of hierarchical user and object attribute groups to ABAC. It is shown that HGABAC is capable of representing the traditional models of access control (MAC, DAC and RBAC) using this group hierarchy and that in many cases it’s use simplifies both attribute and policy administration. HGABAC serves as the basis upon which extensions are built to incorporate delegation into ABAC. Several potential strategies for introducing delegation into ABAC are proposed, categorized into families and the trade-offs of each are examined. One such strategy is formalized into a new User-to-User Attribute Delegation model, built as an extension to the HGABAC model. Attribute Delegation enables users to delegate a subset of their attributes to other users in an off-line manner (not requiring connecting to a third party). Finally, a supporting architecture for HGABAC is detailed including descriptions of services, high-level communication protocols and a new low-level attribute certificate format for exchanging user and connection attributes between independent services. Particular emphasis is placed on ensuring support for federated and distributed systems. Critical components of the architecture are implemented and evaluated with promising preliminary results. It is hoped that the contributions in this research will further the acceptance of ABAC in both academia and industry by solving the problem of delegation as well as simplifying administration and policy authoring through the introduction of hierarchical user groups

Social Network Analysis with sna

Modern social network analysis---the analysis of relational data arising from social systems---is a computationally intensive area of research. Here, we provide an overview of a software package which provides support for a range of network analytic functionality within the R statistical computing environment. General categories of currently supported functionality are described, and brief examples of package syntax and usage are shown.

Analysis and Design Security Primitives Based on Chaotic Systems for eCommerce

Security is considered the most important requirement for the success of electronic commerce, which is built based on the security of hash functions, encryption algorithms and pseudorandom number generators. Chaotic systems and security algorithms have similar properties including sensitivity to any change or changes in the initial parameters, unpredictability, deterministic nature and random-like behaviour. Several security algorithms based on chaotic systems have been proposed; unfortunately some of them were found to be insecure and/or slow. In view of this, designing new secure and fast security algorithms based on chaotic systems which guarantee integrity, authentication and confidentiality is essential for electronic commerce development. In this thesis, we comprehensively explore the analysis and design of security primitives based on chaotic systems for electronic commerce: hash functions, encryption algorithms and pseudorandom number generators. Novel hash functions, encryption algorithms and pseudorandom number generators based on chaotic systems for electronic commerce are proposed. The securities of the proposed algorithms are analyzed based on some well-know statistical tests in this filed. In addition, a new one-dimensional triangle-chaotic map (TCM) with perfect chaotic behaviour is presented. We have compared the proposed chaos-based hash functions, block cipher and pseudorandom number generator with well-know algorithms. The comparison results show that the proposed algorithms are better than some other existing algorithms. Several analyses and computer simulations are performed on the proposed algorithms to verify their characteristics, confirming that these proposed algorithms satisfy the characteristics and conditions of security algorithms. The proposed algorithms in this thesis are high-potential for adoption in e-commerce applications and protocols

An improved penalty algorithm using model order reduction for MIPDECO problems with partial observations

This work addresses optimal control problems governed by a linear time-dependent partial differential equation (PDE) as well as integer constraints on the control. Moreover, partial observations are assumed in the objective function. The resulting problem poses several numerical challenges due to the mixture of combinatorial aspects, induced by integer variables, and large scale linear algebra issues, arising from the PDE discretization. Since classical solution approaches such as the branch-and-bound framework are typically overwhelmed by such large-scale problems, this work extends an improved penalty algorithm proposed by the authors, to the time-dependent setting. The main contribution is a novel combination of an interior point method, preconditioning, and model order reduction yielding a tailored local optimization solver at the heart of the overall solution procedure. A thorough numerical investigation is carried out both for the heat equation as well as a convection-diffusion problem demonstrating the versatility of the approach

Cube attacks on cryptographic hash functions

Cryptographic hash functions are a vital part of our current computer sys- tems. They are a core component of digital signatures, message authentica- tion codes, file checksums, and many other protocols and security schemes. Recent attacks against well-established hash functions have led NIST to start an international competition to develop a new hashing standard to be named SHA-3. In this thesis, we provide cryptanalysis of some of the SHA-3 candidates. We do this using a new cryptanalytical technique introduced a few months ago called cube attacks. In addition to summarizing the technique, we build on it by providing a framework for estimating its potential effectiveness for cases too computationally expensive to test. We then show that cube at- tacks can not only be applied to keyed cryptosystems but also to hash func- tions by way of a partial preimage attack. We successfully apply this attack to reduced-round variants of the ESSENCE and Keccak SHA-3 candidates and provide a detailed analysis of how and why the cube attacks succeeded. We also discuss the limits of theoretically extending these attacks to higher rounds. Finally, we provide some preliminary results of applying cube attacks to other SHA-3 candidates