Search Results (3)

The conjunctive normal form (CNF) algorithm is one of the best known and most widely used algorithms in classical logic and its applications. In its algebraic approach, it makes use in a loop of a certain well-defined operation related to the “distributivity” of logical disjunction versus conjunction. For those types of implementations, the loop iteration runs a comparison between formulas to decide when to stop. In this article, we explain how to pre-calculate the exact number of loop iterations, thus avoiding the work involved in the above-mentioned comparison. After that, it is possible to concatenate another loop focused now on the “associativity” of conjunction and disjunction. Also for that loop, we explain how to calculate the optimal number of rounds, so that the decisional comparison phase for stopping can be also avoided. Full article

Hyper-graphs offer the opportunity to formulate logical statements about their components, for example, using Horn clauses. Several models of Information Systems can be represented using hyper-graphs as the workflows, i.e., the business processes. During the modeling of Information Systems, many constraints should be maintained during the development process. The models of Information Systems are complex objects, for this reason, the analysis of algorithms and graph structures that can support the consistency and integrity of models is an essential issue. A set of interdependencies between models and components of architecture can be formulated by functional dependencies and can be investigated via algorithmic methods. Information Systems can be perceived as overarching documents that includes data collections; documents to be processed; and representations of business processes, activities, and services. Whe selecting and working out an appropriate method encoding of artifacts in Information Systems, the complex structure can be represented using hyper-graphs. This representation enables the application of various model-checking, verification, and validation tools that are based on formal approaches. This paper describes the proposed representations in different situations using hyper-graphs, moreover, the formal, algorithmic-based model-checking methods that are coupled with the representations. The model-checking methods are realized by algorithms that are grounded in graph-theoretical approaches and tailored to the specificity of hyper-graphs. Finally, the possible applications in a real-life enterprise environment are outlined. Full article

A differential fault attack framework for the Enocoro family of stream ciphers is presented. We only require that the attacker can reset the internal state and inject a random byte-fault, in a random register, during a known time period. For a single fault injection, we develop a differential clocking algorithm that computes a set of linear equations in the in- and output differences of the non-linear parts of the cipher and relates them to the differential keystream. The usage of these equations is two-fold. Firstly, one can determine those differentials that can be computed from the faulty keystream, and secondly they help to pin down the actual location and timing of the fault injection. Combining these results, each fault injection gives us information on specific small parts of the internal state. By encoding the information we gain from several fault injections using the weighted Horn clauses, we construct a guessing path that can be used to quickly retrieve the internal state using a suitable heuristic. Finally, we evaluate our framework with the ISO-standardized and CRYPTREC candidate recommended cipher Enocoro-128v2. Simulations show that, on average, the secret key can be retrieved within 20 min on a standard workstation using less than five fault injections. Full article