Software-dened networking (SDN) is an approach to building computer net- works that separate and abstract data planes and control planes of these systems. In a SDN a centralized controller manages a distributed set of switches. A set of open commands for packet forwarding and ow-table updating was dened in the form of a protocol known as OpenFlow. In this paper we describe an abstract formal model of SDN, introduce a tentative language for specication of SDN forwarding policies, and set up formally model-checking problems for SDNs.
The authors of [1, 2] suggested a model of information distortion by white noise. The present work discusses the asymptotic behavior of CRC error probabilities at low values of p, which is the probability of distortion of transferred information bits. On the basis of the theoretical results in two specific protocols—Е1 and ETSI EN 302307—as well as in the examples, the probability values for the error in recognizing the given packet as nondistorted in the presence of at least one distortion are assessed.
We study the value distributions for the control cyclic redundancy check (CRC) of length k, drawn at the data section of volume n. The behavior of CRC value distribution is examined at large n and fixed values of k (k = const, n → ∞). With the application of the character theory, we find the conditions of asymptomatic uniformity of the CRC distribution. The asymptomatic results can be applied during the assessment of errors of a series of protocols such as USB, X.25, HDLC, Bluetooth, Ethernet, etc.
In this work, we yield an attainable upper estimate of the degree of distinguishability of a connected permutation automaton with an assigned diameter.
Nested Petri nets (NP-nets) is an extension of Petri net formalism within the “nets-within-nets” approach, when tokens in a marking are Petri nets wich have autonomous behavior and synchronize with the system net. The formalism of NP-nets allows modeling multilevel multiagent systems with dynamic structure in a natural way. Currently there is no tool support for NP-nets simulation and analysis. The paper proposes translation of NP-nets into colored Petri nets and using CPN Tools as a virtual machine for NP-nets modeling, simulation and automatic verification.
We consider error probabilities in protocols using CRC to detect distortions in transmitted batches. A probability-theory model of an additive long-term noise is constructed as a sequence of independent noise blocks of a prescribed length. We show that there are conditions to be imposed on the form of the k-order polynomial forming the CRC and on block size s such that the error probability α is close to 2−k and does not depend on s provided that distortion probability P1 is high.
Process mining is a new direction in the field of modeling and analysis of processes, where an important role is played by the use of information from event logs that describe the history of the system behavior. Methods and approaches used in process mining are often based on various heuristics, and experiments with large event logs are crucial for substantiating and comparing developed methods and algorithms. These experiments are very time consuming, so automation of experiments is an important task in the field of process mining. This paper presents the DPMine language developed specifically to describe and carry out process mining experiments. The basic concepts of the DPMine language as well as principles and mechanisms of its extension are described. Ways of integration of the DPMine language as dynamically loaded components into the VTMine modeling tool are considered. A sample experiment of building a fuzzy model of a process from a data log stored in a normalized database is given.
To verify realtime properties of UML statecharts one may apply a UPPAAL, toolbox for model checking of realtime systems. One of the most suitable ways to specify an operational semantics of UML statecharts is to invoke the formal model of Hierarchical Timed Automata. Since the model language of UPPAAL is based on Networks of Timed Automata one has to provide a conversion of Hierarchical Timed Automata to Networks of Timed Automata. In this paper we describe this conversion algorithm and prove that it is correct w.r.t. UPPAAL query language which is based on the subset of Timed CTL.
The intent of this paper is to describe a static analysis tool under development. The main idea behind the design of this tool is to use type and effect systems for static analysis of real programs. The tool uses LLVM bitcode files as input, thus extending the set of analyzed languages to those supported by LLVM compiler infrastructure. It uses its own parser of bitcode files and a program model similar to that of LLVM. The approach taken is to research feasibility of designing instruments for static analysis by applying known type and effect system based algorithms for detecting defects to LLVM bitcode language and effectively to original source code
The paper considers methods of program transformation equivalent to optimizing the cycle invariant, applied to the functional data-flow model implemented in the Pifagor programming language. Optimization of the cycle invariant in imperative programming languages is reduced to a displacement from the cycle of computations that do not depend on variables that are changes in the loop. A feature of the functional data flow parallel programming language Pifagor is the absence of explicitly specified cyclic computations (the loop operator). However, recurring calculations in this language can be specified recursively or by applying specific language constructs (parallel lists). Both mechanisms provide the possibility of parallel execution. In the case of optimizing a recursive function, repeated calculations are carried out into an auxiliary function, the main function performing only the calculation of the invariant. When optimizing the invariant in computations over parallel lists, the calculation of the invariant moves from the function that executes over the list items to the function containing the call. The paper provides a definition of “invariant” applied to the Pifagor language, algorithms for its optimization, and examples of program source codes, their graph representations (the program dependence graph) before and after optimization. The algorithm shown for computations over parallel lists is applicable only to the Pifagor language, because it rests upon specific data structures and the computational model of this language. However, the algorithm for transforming recursive functions may be applied to other programming languages.
A wireless network being affected by a broadcast storm attack has been considered to determine the availability of autonomous nodes and its ability to perform functional tasks under information influence. The conditions for the hacker attacks from a potential intruder have been determined. A wireless device availability analysis has been carried out. A model for determining the technical characteristics of the wireless self-organizing network device has been proposed.
Process mining is a new emerging discipline related to process management, formal process models, and data mining. One of the main tasks of process mining is the model synthesis (discovery) based on event logs. A wide range of algorithms for process model discovery, analysis, and enhancement is developed. The real-life event logs often contain noise of different types. In this paper we describe the main causes of noise in the event logs and study the effect of noise on the performance of process discovery algorithms. The experimental results of application of the main process discovery algorithms to artificial event logs with noise are provided. Specially generated event logs with noise of different types were processed using the four basic discovery techniques. Although modern algorithms can cope with some types of noise, in most cases, their use does not lead to obtaining a satisfactory result. Thus, there is a need for more sophisticated algorithms to deal with noise of different types.
One of the most simple models of computation which is suitable for representation of reactive systems behaviour is a nite state transducer which operates over an input alphabet of control signals and an output alphabet of basic actions. A behaviour of such a reactive system displays itself in the correspondence between ows of control signals and compositions of basic actions performed by the system. We believe that behaviour of this kind requires more suitable and expressive means for formal speci cations than conventional LTL. In this paper we de ne some new (as far as we know) extension LP-LTL of Linear Temporal Logic speci cally intended for describing the properties of transducers computations. In this extension the temporal operators are parameterized by sets of words (languages) which represent distinguished flows of control signals that impact on a reactive system. Basic predicates in our variant of temporal logic are also languages in the alphabet of basic actions of a transducer; they represent the expected response of a transducer to the specified environmental influences. In our earlier papers we considered model checking problem for LP-LTL and LP-CTL and showed that this problem has effective solutions. The aim of this paper is to estimate the expressive power of LP-LTL by comparing it with some well known logics widely used in computer science for specification of reactive systems behaviour. We discovered that a restricted variant LP-1-LTL of our logic is more expressive than LTL and another.
Finite state transducers over semigroups are regarded as a formal model of sequential reactive programs that operate in the interaction with the environment. At receiving a piece of data a program performs a sequence of actions and displays the current result. Such programs usually arise at implementation of computer drivers, on-line algorithms, control procedures. In many cases verification of such programs can be reduced to minimization and equivalence checking problems for finite state transducers. Minimization of a transducer over a semigroup is performed in three stages. At first the greatest common left-divisors are computed for all states of a transducer, next a transducer is brought to a reduced form by pulling all such divisors ''upstream'', and finally a minimization algorithm for finite state automata is applied to the reduced transducer.
First-order program schemata represent one of the most simple models of sequential imperative programs intended for solving verification and optimization problems. We consider the decidable relation of logical–thermal equivalence on these schemata and the problem of their size minimization while preserving logical–thermal equivalence. We prove that this problem is decidable. Further we show that the first-order program schemata supplied with logical–thermal equivalence and finite-state deterministic transducers operating over substitutions are mutually translated into each other. This relationship makes it possible to adapt equivalence-checking and minimization algorithms developed in one of these models of computation to the solution of the same problems for the other model of computation. In addition, on the basis of the discovered relationship, we describe a subclass of first-order program schemata such that minimization of the program schemata from this class can be performed in polynomial time by means of known techniques for minimization of finitestate transducers operating over semigroups. Finally, we demonstrate that in the general case the minimization problem for finite-state transducers over semigroups may have several non-isomorphic solutions.
One of the most serious problems when doing program analyses is dealing with function calls. While function inlining is the traditional approach to this problem, it nonetheless suffers from the increase in analysis complexity due to the state space explosion. Craig interpolation has been successfully used in recent years in the context of bounded model checking to do function summarization which allows one to replace the complete function body with its succinct summary and, therefore, reduce the complexity, but unfortunately this technique can be applied only to a pair of unsatisfiable formulae. In this work-in-progress paper we present an approach to function summarization based on Craig interpolation that overcomes its limitation by using random model sampling. It captures interesting input/output relations, strengthening satisfiable formulae into unsatisfiable ones and thus allowing the use of Craig interpolation. Evaluation results show the applicability of this approach; in our future work we plan to do a more extensive evaluation on real-world examples. © 2015, Allerton Press, Inc.
Abstract—The paper presents calculations of the amount of effort and the reliability of the method of
brute-force attack on a cipher using a statistical criterion for plaintexts, which has type 1 and type 2 errors.
Calculated values of parameters of the discussed cryptanalysis methods for a cipher allows better pre-
dictions of its remaining safe operational life taking into account statistical characteristics for recog-
nizing the plaintext and changes in the communication channel parameters.
The asymptotics of spatially inhomogeneous periodic solutions of the complex, spatially distributed Hutchinson equation with periodic boundary conditions are presented. It is shown that such solutions are observable in a numerical experiment.