Network trust management in emergency situations

We study the unique trust management, and more precisely reputation management and revocation of malicious nodes in the context of ad hoc networks used for emergency communications.Unlike in centralized systems, reputation management and revocation in ad hoc networks is non-trivial. This difficulty is due to the fact that the nodes have to collaboratively calculate the reputation value of a particular node and then revoke the node if the reputation value goes below a threshold. A major challenge in this scheme is to prevent a malicious node from discrediting other genuine nodes. The decision to revoke a node has to be communicated to all the nodes of the network. In traditional ad hoc networks the overhead of broadcasting the message throughout the network may be very high. We solve the problem of reputation management and node revocation in ad hoc networks of cell phones by using a threshold cryptography based scheme. Each node of the network would have a set of anonymous referees, which would store the reputation information of the node and issue reputation certificates to the node with timestamps. The misbehavior of a particular cell phone is reported to its anonymous referees, who issue certificates which reflect the positive and negative recommendations.     

A web-based e-learning system for increasing study efficiency by stimulating learner’s motivation

Due to the opportunities provided by the Internet, more and more people are taking advantage of distance learning courses and during the last few years enormous research efforts have been dedicated to the development of distance learning systems. So far, many e-learning systems are proposed and used practically. However, in these systems the e-learning completion rate is about 30%. One of the reasons is the low study desire when the learner studies the learning materials. In this research, we propose an interactive Web-based e-learning system. The purpose of our system is to increase the e-learning completion rate by stimulating learner’s motivation. The proposed system has three subsystems: the learning subsystem, learner support subsystem, and teacher support subsystem. The learning subsystem improves the learner’s study desire. The learner support subsystem supports the learner during the study, and the teacher support subsystem supports the teacher to get the learner’s study state. To evaluate the proposed system, we developed several experiments and surveys. By using new features such as: display of learner’s study history, change of interface color, encourage function, ranking function, self-determination of the study materials, and grouping of learners, the proposed system can increase the learning efficiency.

Artificial intelligence control for trust-based detection of attackers in 5G social networks

This study introduces a comprehensive framework designed for detecting and mitigating fake and potentially threatening user communities within 5G social networks. Leveraging geo-location data, community trust dynamics, and AI-driven community detection algorithms, this framework aims to pinpoint users posing potential harm. Including an artificial control model facilitates the selection of suitable community detection algorithms, coupled with a trust-based strategy to effectively identify and filter potential attackers. A distinctive feature of this framework lies in its ability to consider attributes that prove challenging for malicious users to emulate, such as the established trust within the community, geographical location, and adaptability to diverse attack scenarios. To validate its efficacy, we illustrate the framework using synthetic social network data, demonstrating its ability to distinguish potential malicious users from trustworthy ones.     

Narrowband frequency-selective up-link and down-link evaluation of daily personal-exposure induced by wireless operating networks

The aim of the study is to present a frequency-selective evaluation of personal exposure induced by wireless operating networks in typical daily environments, derived by analysis of 1,905,162 samples of electric field strength, taken at a 5-s sampling interval. Measurements were collected with calibrated isotropic three-axial electric field probe personal exposure meters operating in the frequency range 88–5850 MHz. ‘’To estimate the electric field distribution below the measurement equipment detection limit, the robust regression on order statistics method was applied, enabling determination of mean values of electric field strength per wireless technology for: home, office, transport, outdoor, and leisure environments. The highest value of total electric field strength exposure is obtained on public transport (buses) followed by coffee shops and outdoor environments, whereas the lowest values are captured in home and office environments. Most of the mean values of the electric field were less than 0.06 V/m. Furthermore, the analyses between the contribution of uplink and downlink exposures for operating wireless cellular networks are given, including a comparison of uplink and downlink electric field levels from other countries. Readings of the 24-h personal-exposure pattern, reveal the GSM + UMTS downlink and Wi-Fi as dominant exposure contributors. The results of this study show that spatial and temporal exposure levels in Kosovo are comparable to those reported for other European countries and far below the international safety guidelines and exposure limits.     

Fast autonomous system traceback

Service-oriented computing (SOC) due to their distributed and lose coupled nature are very vulnerable to distributed denial of service (DDoS) attacks. IP spoofing makes it difficult for the victim to determine the packet's origin. There is a need for a mechanism that could enable real-time traceback of the origins of the attacks. In this paper, we propose a novel protocol, fast autonomous system traceback (FAST) to traceback to the attack originating autonomous systems (AS). The multifold advantages of FAST include reconstruction requires just around 5–10 packets and reconstruction takes just a few seconds. We validate the performance through extensive simulations over the datasets obtained from traceroute.     

Indoor exposure of population to radon in the FYR of Macedonia

The authors present the results of a year-long survey of the indoor radon concentration levels in the FYR of Macedonia. A total number of 437 dwellings in eight statistical regions were subject to radon concentration measurements by using CR-39 track detectors. The annual mean indoor radon concentration in each measuring site was estimated from the four individual measurements with 3 months duration. The measuring period was from December 2008 to December 2009. The distribution of the results was nearly log-normal. The arithmetic and geometric mean values of the annual mean value of radon concentration were estimated to be 105 ± 84 and 84*/1.9 Bq m(-3), respectively. The annual effective dose due to indoor exposure to radon in the dwellings was estimated to be 2.1*/1.9 mSv y(-1).     

Real-time all-optical quality of service monitoring by use of correlation and a network protocol to exploit it

We propose to use optical correlation to measure the quality of an optical link in real time, staying completely within the optical domain. We transmit a test signal of 010 and correlate the received (degraded) signal with 010. The strength and shape of the output measure dispersion and attenuation in just 3 bit periods (75 ps at 40 Gb/s) compared with minutes by traditional methods. Correlation becomes feasible owing to the recent development of tapped delay lines with very large numbers of taps. We present simulations showing that this technique can detect attenuation, dispersion, noise, and jitter. With this instantaneous quality-of-service information available to all nodes in a network, new protocols will enable the network to select paths based on quality, allowing service providers to take into account the system's physical impairments when selecting new light paths or when restoring existing ones and to guarantee varying levels of service. We present one such protocol.     

Adaptive Inter Vehicle Communications

Inter Vehicle Communications (IVC) have the potential to significatively increase the safety in our highways. In such communications, the quality and reliability of service becomes a very critical issue. In particular, it is important that in case of emergencies, when the inter vehicle traffic increases exponentially, the message delay should be kept low. We present a reliable hierarchical routing protocol that uses load balancing to keep message delay low even in presence of high level of traffic. Our protocol is based on geographical routing. The protocol is designed for highway travelers but can be used in other mobile ad-hoc scenarios. The highway is divided in virtual cells, which moves as the vehicles moves. The cell members might choose one or more Cell_Leaders that will behave for a certain time interval as Base Stations. We assume that every node knows its geographical position, given by Global Positioning System (GPS) or some other method. Cell_Leaders form a virtual backbone that is used to forward messages among nodes on different cells. The traffic is distributed among Cell_Leaders in order to optimize the communication delay. We study the effect of load balancing in minimizing delay. Our simulation results show that our proposed protocol improves the delay and the network utilization compared to existing inter vehicles protocols.     

Effect of lyoprotectants on β-glucosidase activity and viability of Bifidobacterium infantis after freeze-drying and storage in milk and low pH juices

The benefit of disaccharide protectants for maintaining viability and β-glucosidase activity of Bifidobacterium infantis UV16PR during freeze-drying and storage in different food matrices was investigated. Protectants used were cellobiose, lactose, sucrose and trehalose.