Informatica

Recently, Tzeng proposed a provably secure and fault-tolerant conference-key agreement protocol. It requires only a constant number of rounds to establish a conference key among all honest participants. This article will show that Tzeng’s protocol does not offer forward secrecy. We say that a conference-key agreement protocol offers forward secrecy if the long-term secret key of any participant is compromised and will not result in the compromise of the previously established conference keys. This property is important and has been included in most key agreement protocols and standards. In this paper, an improvement based on Tzeng’s protocol is proposed and it achieves forward secrecy. Under the Diffie–Hellman decision problem assumption and the random oracle model, we show that the proposed protocol can withstand passive attacks and is secure against impersonator’s attacks. The improved protocol requires a constant number of rounds to compute a conference key. The improved protocol provides fault-tolerance.

Since threshold proxy signature has been proposed, all threshold proxy signature schemes are based on the discrete logarithm problems in the modular multiplicative group which has an element g with a large prime order. Nowadays this kind of threshold proxy signature schemes become more and more complex and time-consuming for security and specific requirement. In this paper, we propose a (bilinear) pairing-based threshold proxy signature scheme with known signers, analyze its security and check the following properties the proposed scheme has: non-repudiation, unforgeability, identifiability, distinguishability, verifiability, prevention of misuse of proxy signing right, etc. Moreover, we point out that the proposed scheme is of great efficiency by comparing it with Sun’s and Hsu et al.’s scheme.

Tele-Collaboration will enable users in different locations to collaborate in a shared, simulated environment as if they were in the same physical room. It’s the ultimate synthesis of networking and media technologies to enhance collaborative environments. When participants are Tele-Collaborated, they are able to interact with each other in a shared virtual environment. They are able to query and visualize data stores and steer complex scientific and engineering simulations. This article investigated the transcoding intermediaries required to achieve an effective telecollaboration on the Web as well as on P2P/Grid environments. Both Scene Graphs as used by the virtual SceneBeans and the SVG DOM tree are found to be essential for the transcoding purpose.

The article describes a hierarchical decision making framework for the evaluation and improvement/redesign of composite systems. The framework is based on Hierarchical Morphological Multicriteria Design (HMMD) and corresponding morphological clique problem which realize “partitioning/synthesis macroheuristic”. The system evaluation process consists in hierarchical integration of expert judgment (as ordinal estimates): a method of integration tables or the above-mentioned morphological approach. As a result, ordinal multi-state classification is realized. The system improvement/redesign process is examined as the selection and planning of redesign operations while taking into account operations attributes (e.g., required resources, effectiveness) and binary relations (equivalence, complementarity, precedence) on the operation sets. For modeling the system improvement process several combinatorial optimization models are used (knapsack problem, multiple choice problem, etc.) including HMMD.

In 2001, Tseng, Jan, and Chien proposed an improved version of Peyravian–Zunic’s password authentication scheme based on the Diffie–Hellman scheme. Later, Yang, Chang, and Hwang demonstrated that Tseng–Jan–Chien’s scheme is vulnerable to a modification attack, and then described an improved scheme. In this paper, we show that Yang–Chang–Hwang’s scheme is still vulnerable to a denial-of-service attack and a stolen-verifier attack. In addition, we also propose an improved scheme with better security.

One of the components of the text-to-speech synthesis system is the database of sounds. Two Lithuanian diphone databases in the MBROLA format are presented in this paper. The list of phonemes and the list of diphones necessary for Lithuanian text-to-speech synthesis are described. The problem of phoneme combinations that are not used in the Lithuanian language is dealt with in the work. Also, the article is concerned with transcribing a Lithuanian text.

The paper deals with Knowledge-based Information Systems (IS) engineering. The Enterprise management functions, processes and their interactions are considered as the major components of the domain knowledge. This is the peculiarity of this approach to Enterprise modelling for IS engineering. The resulting framework for Enterprise modelling and Knowledge-based IS engineering – Enterprise meta-model (EMM) – is developed and presented in this paper. The architecture of the advanced CASE system is also discussed in this paper.

The more realistic neural soma and synaptic nonlinear relations and an alternative mean field theory (MFT) approach relevant for strongly interconnected systems as a cortical matter are considered. The general procedure of averaging the quenched random states in the fully-connected networks for MFT, as usually, is based on the Boltzmann Machine learning. But this approach requires an unrealistically large number of samples to provide a reliable performance. We suppose an alternative MFT with deterministic features instead of stochastic nature of searching a solution a set of large number equations. Of course, this alternative theory will not be strictly valid for infinite number of elements. Another property of generalization is an inclusion of the additional member in the effective Hamiltonian allowing to improve the stochastic hill-climbing search of the solution not dropping into local minima of the energy function. Especially, we pay attention to increasing of neural networks retrieval capability transforming the replica-symmetry model by including of different nonlinear elements. Some results of numerical modeling as well as the wide discussion of neural systems storage capacity are presented.

In this paper public available C and C++ packages for interval arithmetic are investigated and experimentally compared. The results of comparison give suggestions which packages and when are preferable.

The aim of the given paper is the development of an approach for parametric identification of Wiener systems with piecewise linear nonlinearities, i.e., when the linear part with unknown parameters is followed by a saturation-like function with unknown slopes. It is shown here that by a simple data reordering and by a following data partition the problem of identification of a nonlinear Wiener system could be reduced to a linear parametric estimation problem. Afterwards, estimates of the unknown parameters of linear regression models are calculated by processing respective particles of input-output data. A technique based on ordinary least squares (LS) is proposed here for the estimation of parameters of linear and nonlinear parts of the Wiener system, including the unknown threshold of piecewise nonlinearity, too. The results of numerical simulation and identification obtained by processing observations of input-output signals of a discrete-time Wiener system with a piecewise nonlinearity by computer are given.