Summary IOTA is a distributed ledger technology with a new structure called Tangle, which offers high scalability, no fees, and near‐instant transfers for the internet‐of‐things (IoT) networks. The most important issue of IOTA is consensus achievement, which is handled by a single node acting as a coordinator. A single and default coordinator node exposes IOTA to the single point of failure and incomplete distribution issues. In this paper, a novel algorithm for selecting multiple coordinators to participate in the consensus process at milestones is proposed (i.e., MCS algorithm) to overcome the problem of a single coordinator in IOTA network. The MCS algorithm is applied in a two‐layered architecture including IoT devices (i.e., Layer 1) and fog nodes (i.e., Layer 2). We define and formulate four different properties as metrics to select multiple coordinators in this architecture. Moreover, a collusion list is defined to decrease the risk of collusion between fog nodes in the network. Experimental results show that using multiple fog nodes as coordinators in IOTA network can improve the average response time and average throughput while does not considerably sacrifice the total cost and system utilization in comparison with the use of a single default coordinator in IOTA network.

Summary DDoS attack as an attempt to make an online service inaccessible by suppressing it with massive traffic from various sources is a problem that is getting worse by the day, and when customers need to implement DDoS mitigation solutions in their network, they often have to make major changes to the existing network in terms of establishing new protocols or the need to completely redesign the existing network. Software evolution in networks under the name of software‐defined networks is developing and advancing in parallel with traditional networks, and the tendency and migration towards this generation of networks may be considered more and more seriously. Using SDN to encounter DDoS attacks, given its reactive capabilities, brings strategies such as dynamic cyber deception and active defense to minds, against attackers. In this article, we show how to obfuscate the network route to the destination by playing the address in the path and destination of the attacker's request, without understanding them from the heart of the issue by using the capabilities of software‐defined networks and lead DDoS attack flows, and kept the rest of network safe with least effect on topology from this destruction.

Abstract Dynamic wireless sensor network (DWSN) is a group of mobile sensor nodes deployed in an intended area. Secure communication in DWSNs depends on the existence of an efficient key management scheme. Because of the movements of sensor nodes and unknown mobility pattern, dynamic key management is an important issue in such networks. In this paper, we propose a new key management scheme, which uses key pre‐distribution and post‐deployment key establishment mechanisms for DWSNs. The proposed approach ensures that the two communicating nodes share at least one common key. It also provides efficient ways for key generation and revocation as well as addition or deletion of mobile sensor nodes. Compared with the other key management schemes, which are designed for DWSNs, our simulation and analytical results demonstrate the efficiency of the proposed approach in terms of confidentiality, resilience, memory usage, energy consumption and overhead. Copyright © 2014 John Wiley & Sons, Ltd.

ABSTRACT Combinatorial designs are powerful mathematical tools with comprehensive and simple algebraic structures. Recently, many researchers have used combinatorial designs as key predistribution schemes in wireless sensor networks (WSNs). Previous studies on security of WSNs are mainly concentrated on those networks containing nodes with the same capabilities. Further, investigations reveal that high reliability and lifetime on networks can be achieved through hierarchical heterogeneous wireless sensor networks, where a small number of sensor nodes have more energy, memory, and transmission capability. Inspired by scheme due to Lee and Stinson, we propose a key predistribution scheme for a clustered heterogeneous WSN using transversal designs. This proposed scheme assigns key chains to sensor nodes before deployment and separates key pool of each cluster by adding a pseudo‐random generated number after deployment. The performance evaluation and security analysis show that our proposed scheme can provide better security with significant reductions on communication overhead and storage space than other key management schemes without compromising connectivity. Copyright © 2014 John Wiley & Sons, Ltd.