Informatica

Conventional Blind Source Separation (BSS) algorithms separate the sources assuming the number of sources equals to that of observations. BSS algorithms have been developed based on an assumption that all sources have non-Gaussian distributions. Most of the instances, these algorithms separate speech signals with super-Gaussian distributions. However, in real world examples there exist speech signals which are sub-Gaussian. In this paper, a novel method is proposed to measure the separation qualities of both super-Gaussian and sub-Gaussian distributions. This study measures the impact of the Probability Distribution Function (PDF) of the signals on the outcomes of both sub and super-Gaussian distributions. This paper also reports the study of impact of mixing environment on the source separation. Simulation improves the results of the separated sources by 7 dB to 8 dB, and also confirms that the separated sources always have super-Gaussian characteristics irrespective of PDF of the signa ls or mixtures.

The paper proposes a novel predictive-reactive planning and scheduling framework in which both approaches are combined to complement each other in a reasonably balanced way. Neither original scheduling algorithms nor original techniques can be find in this paper. It also does not intend to invent new mechanisms or to propose some cardinally new ideas. The aim is to choose, adapt and test ideas, mechanisms and algorithms already proposed by other researchers. The focus of this research is set on make-to-order production environments. The proposed approach aims not only to absorb disruptions in shop floor level schedules but also to mitigate the impacts of potential exceptions, which disrupt mid-term level production plans. It is based on application of risk mitigation techniques and combines various simulation techniques extended by optimization procedures. The proposed approach is indented to be implemented in Advanced Planning and Scheduling system, which is an add-on for Enterprise Resources Planning system. To make it easier to understand the focus of the paper, at the beginning the position from which we start is clarified.

Hwang et al. proposed an ElGamal-like scheme for encrypting large messages, which is more efficient than its predecessor in terms of computational complexity and the amount of data transformation. They declared that the resulting scheme is semantically secure against chosen-plaintext attacks under the assumptions that the decision Diffie–Hellman problem is intractable. Later, Wang et al. pointed out that the security level of Hwang et al.'s ElGamal-like scheme is not equivalent to the original ElGamal scheme and brings about the disadvantage of possible unsuccessful decryption. At the same time, they proposed an improvement on Hwang et al.'s ElGamal-like scheme to repair the weakness and reduce the probability of unsuccessful decryption. However, in this paper, we show that their improved scheme is still insecure against chosen-plaintext attacks whether the system is operated in the quadratic residue modulus or not. Furthermore, we propose a new ElGamal-like scheme to withstand the adaptive chosen-ciphertext attacks. The security of the proposed scheme is based solely on the decision Diffie–Hellman problem in the random oracle model.

In a supervised learning, the relationship between the available data and the performance (what is learnt) is not well understood. How much data to use, or when to stop the learning process, are the key questions.

In this paper robust image authentication integrated with semi-fragile pixel-wise tamper localization is analyzed. A new pixel-wise transformation robust to blurring/sharpening while fragile to all other image processing operations is proposed. A new method featuring binary and percentage measures with novel ability to integrate human opinion for image authenticity evaluation is presented. Protection for all bits in the pixel is advantage as well as small size of the signature – less than 10% of initial image.

Revocation problem is a critical issue for key management of public key systems. Any certificate-based or identity (ID)-based public key systems must provide a revocation method to revoke misbehaving/compromised users from the public key systems. In the past, there was little work on studying the revocation problem of ID-based public key systems. Most recently, Tseng and Tsai presented a novel ID-based public key system with efficient revocation using a public channel, and proposed a practical revocable ID-based encryption (called RIBE). They proved that the proposed RIBE is semantically secure in the random oracle model. Although the ID-based encryption schemes based on the random oracle model can offer better performance, the resulting schemes could be insecure when random oracles are instantiated with concrete hash functions. In this paper, we employ Tseng and Tsai's revocable concept to propose a new RIBE without random oracles to provide full security. We demonstrate that the proposed RIBE is semantically secure against adaptive-ID attacks in the standard model.

Three main approaches presently dominate preferences derivation or evaluation process in decision analysis (selecting, ranking or sorting options, alternatives, actions or decisions): value type approach (a value function or an utility measure is derived for each alternative to represent its adequacy with decision goal); outranking methods (a pair comparison of alternatives are carried up under each attribute or criteria to derive a pre-order on the alternatives set); and decision rules approach (a set of decision rules are derived by a learning process from a decision table with possible missing data). All these approaches suppose to have a single decision objective to satisfy and all alternatives characterized by a common set of attributes or criteria. In this paper we adopt an approach that highlights bipolar nature of attributes with regards to objectives that we consider to be inherent to any decision analysis problem. We, therefore, introduce supporting and rejecting notions to describ attributes and objectives relationships leading to an evaluation model in terms of two measures or indices (selectability and rejectability) for each alternative in the framework of satisficing game theory. Supporting or rejecting degree of an attribute with regard to an objective is assessed using known techniques such as analytic hierarchy process (AHP). This model allows alternatives to be characterized by heteregeneous attributes and incomparability between alternatives in terms of Pareto-equilibria.

Multisignature scheme allows a group of signers to generate a compact signature on a common document that certifies they endorsed the message. However, the existing state of the art multisignatures often suffers from the following problems: impractical key setup assumptions, loose security reductions and inefficient signature verification. In this paper, we propose a non-interactive multisignature scheme with tight security reduction in the random oracle model. Our proposed multisignatures address the above three problems by achieving: provable security in the plain public key model; tight security reduction under the standard Computational Diffie–Hellman (CDH) assumption and 𝒪(1) computational time for signature verification through pre-computation. Hence, our non-interactive multisignatures are of great use in routing authentication of networks.

In this paper, we consider piecewise linear aggregates (PLA) and a possibility to use a linear temporal logic for analysis of their performance over finite structures (finite linear temporal logic (LTL)). We describe a calculus where the search is performed with respect to a context of the formula. An important aspect of finite LTL is the simplicity of its model of time and actions. PLA is used for description of numerous complex systems. The answers about the behavior of the aggregate are got by finding an interpretation in which all the formulas describing the work of the aggregate are true. This is illustrated by formalizing alternative bit protocol (ABP) task. We describe the ABP by putting it in the form of a planning problem. From the obtained model, we can find a finite sequence of actions to be executed in order to achieve the goal. In addition, an alternative bit protocol problem is described using the planning domain description language (PDDL). We report the results of experiments conducted using the LPG-TD planner.

The paper deals with the problem of high-school time-tabling that is important in applications, but hard for solving. The algorithm is presented for timetabling based on Multi-start and Simulated Annealing with parameters adapted using the Bayes approach. The algorithm proposed is compared with other timetabling algorithms using the web-based software. A multi-start algorithm is a simple way to provide the convergence, if the number of uniformly distributed starting points is large. A disadvantage is slow convergence.