Abstract Model Counting: A Novel Approach for Quantification of Information Leaks

acmid: 2590328 keywords: model checking, quantitative information flow, satisfiability modulo theories, symbolic execution location: Kyoto, Japan numpages: 10acmid: 2590328 keywords: model checking, quantitative information flow, satisfiability modulo theories, symbolic execution location: Kyoto, Japan numpages: 10acmid: 2590328 keywords: model checking, quantitative information flow, satisfiability modulo theories, symbolic execution location: Kyoto, Japan numpages: 10We present a novel method for Quantitative Information Flow analysis. We show how the problem of computing information leakage can be viewed as an extension of the Satisfiability Modulo Theories (SMT) problem. This view enables us to develop a framework for QIF analysis based on the framework DPLL(T) used in SMT solvers. We then show that the methodology of Symbolic Execution (SE) also fits our framework. Based on these ideas, we build two QIF analysis tools: the first one employs CBMC, a bounded model checker for ANSI C, and the second one is built on top of Symbolic PathFinder, a Symbolic Executor for Java. We use these tools to quantify leaks in industrial code such as C programs from the Linux kernel, a Java tax program from the European project HATS, and anonymity protocol

Marchés électroniques et hiérarchies électroniques

Electronic links are becoming increasingly important in the inter-and intra-firm spheres. The present article develops an analytical frame for defining this evolution. The growing use of electronic interconnections can be considered as the combination of three forces : the effect of electronic communication, the effect of electronic brokerage and the effect of electronic integration. The nature of these interconnections - electronic hierarchy or electronic market - depends on factors such as the simplicity of product specifications and the degree of product specificity with regard to customers. By reducing co-ordination costs, information technologies lead to global change towards a more widespread use of markets, to the detriment of hierarchies, for the co-ordination of economic activities. By applying this analytical frame, it is possible to forecast some of the changes likely to attend the intensified use of information technologies.Les connections électroniques prennent une place de plus en plus importante à l'intérieur des entreprises et entre les entreprises. Cet article développe un cadre analytique permettant de mieux cerner cette évolution. L'usage croissant des interconnections électroniques peut être considéré comme la combinaison de trois forces : l'effet de communication électronique, l'effet de courtage électronique et l'effet d'intégration électronique. La nature de ces interconnections - hiérarchie électronique ou marché électronique - dépend de facteurs tels que la simplicité des descriptions des produits et le degré de spécificité des produits vis-à-vis des clients. En réduisant les coûts de coordination, les technologies d'information amènent un changement global vers une utilisation plus grande des marchés au détriment des hiérarchies pour assurer la coordination des activités économiques. En appliquant ce cadre analytique, il est possible de prévoir quelques-uns des changements évolutifs qui auront vraisemblablement lieu avec l'intensification de l'usage des technologies d'information.Malone Thomas, Benjamin Robert, Yates Joanne, Communications of the ACM, Perani Jérôme. Marchés électroniques et hiérarchies électroniques. In: Réseaux, volume 15, n°84, 1997. Les coûts de transaction. pp. 21-45

Leakage-Resilient Authentication and Encryption from Symmetric Cryptographic Primitives

Leakage-resilient cryptosystems aim to maintain security in situations where their implementation leaks physical information about their internal secrets. Because of their efficiency and usability on a wide range of platforms, solutions based on symmetric primitives (such as block ciphers) are particularly attractive in this context. So far, the literature has mostly focused on the design of leakage-resilient pseudorandom objects (e.g. PRGs, PRFs, PRPs). In this paper, we consider the complementary and practically important problem of designing secure authentication and encryption schemes. For this purpose, we follow a pragmatic approach based on the advantages and limitations of existing leakage-resilient pseudorandom objects, and rely on the (arguably necessary, yet minimal) use of a leak-free component. The latter can typically be instantiated with a block cipher implementation protected by traditional countermeasures, and we investigate how to combine it with the more intensive use of a much more efficient (less protected) block cipher implementation. Based on these premises, we propose and analyse new constructions of leakage-resilient MAC and encryption schemes, which allow fixing security and efficiency drawbacks of previous proposals in this direction. For encryption, we additionally provide a detailed discussion of why previously proposed (indistinguishability based) security definitions cannot capture actual side-channel attacks, and suggest a relaxed and more realistic way to quantify leakage-resilience in this case, by reducing the security of many iterations of the primitive to the security of a single iteration, independent of the security notion guaranteed by this single iteration (that remains hard to define)

CLAPS: Client-Location-Aware Path Selection in Tor

Much research has investigated improving the security and performance of Tor by having Tor clients choose paths through the network in a way that depends on the client's location. However, this approach has been demonstrated to lead to serious deanonymization attacks. Moreover, we show how in some scenarios it can lead to significant performance degradation. For example, we demonstrate that using the recently-proposed Counter-RAPTOR system when guard bandwidth isn't abundant could increase median download times by 28.7%. We propose the CLAPS system for performing client-location-aware path selection, which fixes the known security and performance issues of existing designs. We experimentally compare the security and performance of CLAPS to Counter-RAPTOR and DeNASA. CLAPS puts a strict bound on the leakage of information about the client's location, where the other systems could completely reveal it after just a few connections. It also guarantees a limit on the advantage that an adversary can obtain by strategic relay placement, which we demonstrate to be overwhelming against the other systems. Finally, due to a powerful formalization of path selection as an optimization problem, CLAPS is approaching or even exceeding the original goals of algorithms to which it is applied, while solving their known deficiencies