Trust evaluation is an effective method to detect malicious nodes and ensure security in wireless sensor networks (WSNs). In this paper, an efficient dynamic trust evaluation model (DTEM) for WSNs is proposed, which implements accurate, efficient, and dynamic trust evaluation by dynamically adjusting the weights of direct trust and indirect trust and the parameters of the update mechanism. To achieve accurate trust evaluation, the direct trust is calculated considering multitrust including communication trust, data trust, and energy trust with the punishment factor and regulating function. The indirect trust is evaluated conditionally by the trusted recommendations from a third party. Moreover, the integrated trust is measured by assigning dynamic weights for direct trust and indirect trust and combining them. Finally, we propose an update mechanism by a sliding window based on induced ordered weighted averaging operator to enhance flexibility. We can dynamically adapt the parameters and the interactive history windows number according to the actual needs of the network to realize dynamic update of direct trust value. Simulation results indicate that the proposed dynamic trust model is an efficient dynamic and attack-resistant trust evaluation model. Compared with existing approaches, the proposed dynamic trust model performs better in defending multiple malicious attacks.
Wireless sensor networks have been studied extensively for their broad range of applications, especially in an environment with no infrastructure. And the nodes failures, link errors, and malicious node attacks are likely to occur quite frequently in wireless sensor networks. It affects the stability and reliability of data transmission. In this paper, we present a security fault-tolerant routing for multi-layer non-uniform clustered wireless sensor networks to improve the security reliability of network operation and data transmission. First, we establish the multi-layer nonuniform clustered network topology, which can effectively avoid the intercluster load imbalance; clustering can effectively reduce the network energy consumption and improve the network reliability. In the cluster head selection process, the trust model and the fuzzy logic are utilized to evaluate the qualification of sensors to become a cluster head. The routing algorithm uses the priority level and the trust value to select the security cluster head as the next hop and builds a route path between the different layers through the cluster head. Secondly, according to the multi-layer of the network topology structure, we present a fault-tolerant algorithm based on rollback strategy. Theoretical analysis and simulations show that the algorithm has the high packet receiving rate by BS and balanced energy consumption. It has good performance in fault tolerance and stability of data transmission, it avoids the hot issue in energy consumption and achieves the network load balance, and it prolongs the entire network life time.
As cloud computing has been popularized massively and rapidly, individuals and enterprises prefer outsourcing their databases to the cloud service provider (CSP) to save the expenditure for managing and maintaining the data. The outsourced databases are hosted, and query services are offered to clients by the CSP, whereas the CSP is not fully trusted. Consequently, the security shall be violated by multiple factors. Data privacy and query integrity are perceived as two major factors obstructing enterprises from outsourcing their databases. A novel scheme is proposed in this paper to effectuate -nearest neighbors (kNN) query and query authentication on an encrypted outsourced spatial database. An asymmetric scalar-product-preserving encryption scheme is elucidated, in which data points and query points are encrypted with diverse encryption keys, and the CSP can determine the distance relation between encrypted data points and query points. Furthermore, the similarity search tree is extended to build a novel verifiable SS-tree that supports efficient query and query verification. It is indicated from the security analysis and experiment results that our scheme not only maintains the confidentiality of outsourced confidential data and query points but also has a lower query processing and verification overhead than the MR-tree.
A suitable e-learning system management needs to carry out a web-information system in order to allow integrated fruition of data and metadata concerning the activities typical of e-learning environment. The definition of an "Information System" for e-learning takes advantage of the potentialities of Web technologies both as for the access to metadata present on the several platforms, and as for the implementation of courseware which make up the relative didactic environment. What information systems have in common is the technological environment on which they are generally implemented and the use of metadata in order to structure information at all cognitive and organization levels. In this work we are going to define a methodology for the implementation of a specific Information System for an e-learning environment.
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