Nicolae Constantinescu

• PhD, Assoc. Prof.
• Professor (Associate) at Lucian Blaga University of Sibiu

Computing systems grouped in subnets use distributed security models, in general, by creating session keys based on the Diffie–Hellman model, and calculating the necessary parameters for this, on each of the systems. In the particular case of a network of devices heterogeneous in terms of computing power, such as IoT, the modeling of a security sys...

This study proposes a hierarchical communication framework for drone swarms designed to enhance security and operational efficiency. Leveraging elliptic curve cryptography and space quanta concepts, the model ensures continuous authentication and risk assessment of participating entities. Experimental results demonstrate the framework’s effectivene...

The detection of clear and encrypted data that are transported through computer networks is of particular importance both for protecting the data and the users to whom they belong and to whom they are intended, as well as the networks through which they are transmitted. The proposed method consists of an algorithm that classifies the data it receiv...

Mathematical models based on elliptic curves have been intensively studied since their applicability in data security systems was discovered. In this article, the authors describe the optimal way to select particular subspaces over which elliptic curves are defined, showing the applicability of these subspaces in secure data transfer. Access to lar...

"The aim of this paper is to provide a characterization diagram for a family of B\'{e}zier flexible interpolation curves as well as to present an application of our results in cryptography. In our interpolation scheme, two parameters, $t_1,\ t_2\in (0,1)$ determine the position of the interpolation points on the B\'{e}zier curve. Consequently we ob...

Starting from the asymmetric encryption general protocols and vulnerability anal- ysers, the present paper illustrate the most important factors, those owning the highest impact level on computation of cryptoperiod of keying data and material, as looked at in a key-compromise impersonation attack scenario. We support our researched list of such fac...

This paper deals with exhibiting and classifying objects along an image sequence. Motion is considered through the image sequence, leading to a frame by frame analysis. We first review a set of methods to detect mobile objects, knowing that our intended perception model is to include colour and get robust the acquisition of flickering images. Objec...

Symmetric cryptographic keys generation systems with a high complexity needs nonlinear mathematical models. This condition is due to the necessity of increasing the complexity of attack on the cryptographic model. In this regard, the present paper takes on a new approach of constructing these systems, having as a starting point combinations based o...

In order to construct the border solutions for nonsupersingular elliptic curve equations, some common used models need to be adapted from linear treated cases for use in particular nonlinear cases. There are some approaches that conclude with these solutions. Optimization in this area means finding the majority of points on the elliptic curve and m...

The main purpose of the cryptography is to find a way to hide the information from the users which do not have the rights to know it, but to reveal to those that have certain things that authorize them to access the contents. In the present article we present a way to accomplish this request by introducing a new way of encryption: by meaning of the...

Starting from the necessity of intelligent access to distributed hierarchically data we construct a system to categorize the users which want to connect to such an organization. The novelty of the solution consist in two factors: first is the way of hierarchy construction which is done not only by authentication and the second reside from the level...

Using a fuzzy logic control system, we propose in this paper an optimized method to reduce the points number to be used in order to identify a person using fuzzy fingerprints. Two fingerprints are similar if n out of N points from the skin are identical. We discuss a criteria to choose these points. Our method compares two matching sets and selects...

The development of the notion of computer system led to a parallel development of the information models of defense stored in these. In parallel it was created an arsenal of access to information without having this right. The first stage is cryptography, the second cryptographic analysis. In these two worlds "parallel in terms of declarative, but...

In any communication process the most important stage is represented by the authentication. If this stage ends successfully, the authenticated part can perform all operations for which it was given permission. So, along with the authentication, this process also informs the authenticated part what are its rights and its restrictions on the system....

Aiming to extend relational databases while preserving their declarative program-ming style, deductive databases support a rule-based language capable of expressing com-plete applications. Distributed deductive databases have been intensively studied in the past decades mainly because they provide a high level for protecting voluminous data with lo...

This paper presents an optimized method to reduce the points number to be used in order to identify a person using fuzzy fingerprints. Two fingerprints are similar if n out of N points from the skin are identical. We discuss the criteria used for choosing these points. We also describe the properties of fuzzy logic and the classical methods applied...

The problem of using legacy information systems by making their services publicly available from the Web has become a tedious one due to the diversity of platforms (operating systems, programming languages, database management systems) on which they were implemented. In this paper we present an online system, WebKM, following the client-server para...

Distributed deductive databases have become more and more popular in the past decade. Their importance is mainly due to their low costs and the high level of protecting data. For such a database there must be secured all the remote database fragments and the infrastructure in order to provide a high security level and to avoid an impersonation. We...

Fuzzy logic was introduced as a mathematical treatment for vague information, being very important in cryptography mostly because its appliance in authentication process. We propose an identity authentication and a key agreement protocol based on fuzzy logic which is recommended for group communication. The users authenticate themselves to a server...

Databases are a central component of e-business applications. They provide the storage and functional facilities (i.e. accessing transactional information) of commercial systems. This paper analyzes database models for e-commerce applications, and studies access constraints necessary to preserve the consistency of data; in particular, access scenar...

One of the most used cryptosystems in the world is the RSA system. Its popularity is due to its high security level. In the last decades, studies have shown that the cryptosystems based on elliptic curves have the same security level as the RSA system. Besides that, elliptic curve cryptosystems have a higher efficiency and they use shorter keys. In...

A genetic algorithm method was used to study the economic and ecological impact of hunting activities using a Genetic Algorithm approach, applied for a version of the Stauffer – Newmann model, adapted for a particular case of a Natural Resource Economics problem: the decision about the intensity of exploitation of hunted species.

Elliptic curve cryptography provides a higher performance than the classic cryptography mainly because shorter keys are used. This paper presents the basics of the elliptic curves, emphasizing the advantage of using them in ecommerce cryptography, this implies a certain level of fields definition for them. We also present several algorithms for sca...

This paper presents CELICA, a multi-agent system for efficient communication in e-commerce environments. The system is based on a hierarchical approach for exchanging information among agents. Our approach uses logarithmic search techniques, thus providing improved behavior in comparison with traditional linear search methods. We present system enh...

The authentication protocols based on classic cryptography use public-key cryptosystems for establishing the common key. Some of them have been proven to be secure but they require a high amount of resources and they need large keys. Applying an elliptic curve authentication protocol, the memory and the power consumption are lower. Another advantag...

Correlation is a statistical method used to determine relationships between two or more variables. The intensities of various factors influence the change in time and space conditions such that the evolution of the dependent phenomena is changing compared with the previous trends. This paper presents a study on the correlations between three very i...

One of the main problems in cryptography is to give criteria to provide good comparators of cipher systems. The security of a cipher system must include the security of the algorithm, the security of the key generator and management module (see [BM94], [CM97],[Mau92a]) and the security of the cryptographic key agreement protocol (see [Mau93a],[MC94...

Fan and Lei proposed an user efficient blind signature scheme based on quadratic residues. The main merit of this scheme is that only a few number of arithmetic modular operations are required for a user to get a legal signature. Therefore, it is very suitable for commerce applications. However, Shao pointed out that this scheme did not achieve the...

This paper is closely related to the problem of finding elements having certain positions resulted after merging between two or more result sets. The problem is encountered frequently nowadays, a typical situation being a business distributed environment i.e. SOA approach, where as a direct consequence of aWeb search, each participating entity will...

In cryptography, linear feedback shift registers (LFSRs) are often used, mainly because they are extremely fast and easy to implement. LFSRs do not offer high security, but there are some generators that use a combination of several LFSRs’ outputs in order to obtain a more secure keystream. In this paper, such a generator which is based on the comp...

One actual problem in cryptography is to find a generator which must carry out some conditions asked by the beneficiary. Some interesting and new results concerning the complexity of the combinations of linear feedback shift registers are presented [B. Schneier, Applied cryptography. Protocols, algorithms and source code in C. 2nd ed. New York, NY:...

Based on the blind signature scheme, it is discussed the way in which a finite set of users which want to communicate over a network, agreed on a symmetrical encryption and the way in which this key is created. The paper will review a solution in which the two parties are authenticated, based on a secret knowledge and a random string which could be...

Choosing the right data structure has been proved many times to have a major role toward design of an optimal algorithm. In this paper, we will present two classical algorithms (together with their associated classical data structures, array and linked list) for finding the (n;m)-Josephus permutations, our contribution being materialized in the thi...

A fundamental challenge in modern cryptography is the establishment of rigorous criteria for effectively comparing cipher systems. A comprehensive security assessment must encompass the strength of the encryption algorithm, the reliability of the key generation process, the robustness of key management components, and the security guarantees of the...

Let E be an elliptic curve. Starting from its definition we create a set of restrictions which helps us to realize an implementation in a real system of the theories concerning the infeasibility of the ECDL problem. We also present the implementation methods to compute the necessary parameters in such a system.

In this paper the way to communicate over a network by two parties, how to agree on a symmetrical encryption and how a cryptographic key is created will be discussed. The paper review a new proposed method, starting from sharing a common information. The difference reside in the way the information is combined inside the original image. Starting fr...

The knowledge grid provides us with the means to represent, share and manage globally distributed knowledge resources over the Internet. The process of analyzing geographically distributed large data sets for extracting novel and interesting patterns or models has become a major challenge during the last years. The knowledge grid infrastructure all...

Several approaches generalizing association rules to fuzzy association rules have been proposed, so far. The quality measures have also been generalized. Such a measure is based on the so-called S-implicator. In this paper we point out some other implicators which can substitute the S-implicator in order to define new support measures which evaluat...

This paper treats the way in which a symmetric cryptographic key, which has been acknowledged by the two counterparts on a communications network, is being created. We treat the manner in which the two will authentify their selfs by using secret information and arbitrary strings, which can be the names of the two. On these strings other data that w...

Existing methods of information extraction from HTML documents include manual approach, supervised learning and automatic techniques. The manual method has high precision and recall values but it is difficult to apply it for large number of pages. Supervised learning involves human interaction to create positive and negative samples. Automatic tech...

The fast development of the World Wide Web makes searching and retrieving of information to become a not easy task. Two algorithms proposed around the fall of 1996, Page Rank [3] and HITS [9], became the center of majority research efforts. They try to remedy the abundance of results, bringing order with the help of notions related to prestige in s...

Existing methods of information extraction from HTML documents include manual approach, supervised learning and automatic techniques. The manual method has high precision and recall values but it is difficult to apply it for large number of pages. Supervised learning involves human interaction to create positive and negative samples. Automatic tech...

vol. 106

In this paper the authors present two protocols for the common key establishment. The first protocol, which has two steps, assures the authentication of the common agree- ment key. The second one is a three-pass authenticated agreement key protocol and it contains a step for the key confirmation. The security of both protocols results from the elli...

Data mining, also known as knowledge discovery in databases, is the process of discovery potentially useful, hidden knowledge or relations among data from large databases. An important topic in data mining research is concerned with the discovery of association rules. The majority of databases are distributed nowadays. In this paper is presented an...

Distributed data mining is the process of analyzing geographically distributed large data sets for extracting patterns or models. An important topic in data mining research is concerned with the discovery of association rules. The majority of databases are distributed nowadays. In this paper, an algorithm for mining fuzzy association rules from dis...

This paper is closely related to the web structure analysis based on visual representation direction, a new and promising one, from which many web application such as information retrieval, information extraction can take advantage of. Page segmentation can be used to improve the query process in information retrieval, to simplify the work of autom...

In this paper we propose a protocol for authenticated key agreement between parties of a computer network. We consider a public-key encryption scheme for authentication and an elliptic-curves-system-based for key-agreement. The presented protocol needs two communication rounds between involved parties and its security is based on the elliptic curve...

In practice, a public-key cryptosystem consists of three parts. First: trusted parts, which provide a safe storage for public key and identification name to every person of the system. Second: a software system, to generate public and secret key for every user that exists in the secure-network. Third: a software, to encrypt and decrypt messages. Th...

The linear complexity of a sequence is the size of the shortest feedback drift register, which generates the sequence. A method of estimating this complexity consists in successive processing of the sequence and obtaining a monotone increasing sequence of estimators (linear complexity profile), of which the limit is the linear complexity. The resul...

Vol. 103

vol. 105