Network flow is susceptible to disruption through a software-defined network caused by malicious switches. The malicious behaviors such as dropping traffic, adding or delaying traffic are diverse. Once a switch is compromised by an attacker, the switch could be malfunctioning or configured incorrectly. In this paper, we propose a real-time method of detecting compromised SDN switches based on chaotic analysis of network traffic. An ARIMA model is used to predict the number of flows in every following three seconds. Then, by calculating the maximum Lyapunov exponent, the chaotic behavior of prediction error time-series is analyzed. Simulation findings indicate that 99.63% of traffic states can be accurately classified by the proposed algorithm.

Group key management (GKM) in mobile communication is important to enable access control for a group of users. A major issue in GKM is how to minimize the communication cost for group rekeying. To design the optimal GKM, researchers have assumed that all group members have the same leaving probabilities and that the tree is balanced and complete to simplify analysis. In the real mobile computing environment, however, these assumptions are impractical and may lead to a large gap between the impractical analysis and the measurement in real-life situations, thus allowing for GKM schemes to incorporate only a specific number of users. In this paper, we propose a new GKM framework supporting more general cases that do not require these assumptions. Our framework consists of two algorithms: one for initial construction of a basic key-tree and another for optimizing the key-tree after membership changes. The first algorithm enables the framework to generate an optimal key-tree that reflects the characteristics of users’ leaving probabilities, and the second algorithm allows continual maintenance of communication with less overhead in group rekeying. Through simulations, we show that our GKM framework outperforms the previous one which is known to be the best balanced and complete structure.

With the emergence of diverse group-based services, multiple multicast groups are likely to coexist in a single network, and users may subscribe to multiple groups simultaneously. However, the existing group key management (GKM) schemes, aiming to secure communication within a single group, are not suitable in multiple multicast group environments because of inefficient use of keys, and much larger rekeying overheads. In this paper, we propose a new GKM scheme for multiple multicast groups, called the master-key-encryption-based multiple group key management (MKE-MGKM) scheme. The MKE-MGKM scheme exploits asymmetric keys, i.e., a master key and multiple slave keys, which are generated from the proposed master key encryption (MKE) algorithm and is used for efficient distribution of the group key. It alleviates the rekeying overhead by using the asymmetry of the master and slave keys, i.e., even if one of the slave keys is updated, the remaining ones can still be unchanged by modifying only the master key. Through numerical analysis and simulations, it is shown that the MKE-MGKM scheme can reduce the storage overhead of a key distribution center (KDC) by 75 percent and the storage overhead of a user by up to 85 percent, and 60 percent of the communication overhead at most, compared to the existing schemes.

Although lots of research efforts have focused on group key management (GKM) for secure multicast, existing GKM schemes are inadequate for vehicle communication (VC) systems since they incur unnecessary rekeying overhead without considering the characteristics of VC systems such as Vehicle-to-Infrastructure communications and a great number of high mobility vehicles. Therefore, we propose a GKM scheme, called RSU-based decentralized key management (RDKM), dedicated for the multicast services in the VC systems. The RDKM scheme significantly reduces the rekeying overhead through delegating a part of the key management functions to the road-side infrastructure units (RSUs) and through updating the key encryption keys (KEKs) within a RSU. The performance of the RDKM scheme is analyzed in terms of communication overhead and storage overhead each of which has a strong impact on the performance of GKM. Furthermore, we propose an optimization algorithm that minimizes the weighted sum of the communication and the storage overhead, called the GKM overhead (GKMO), by appropriately determining the design parameters. The numerical results from the extensive analysis demonstrate that the RDKM scheme outperforms the existing GKM schemes in terms of the GKMO.

A logical key hierarchy (LKH) based key managementapproach is the most common way to manage a group keywith less rekeying overhead. However, the LKH approach causes inefficiency of rekeying the group key in mobile cellular networks since it does not consider the characteristics of the networks, such as the cell-based network topology and the user's mobility. This paper proposes an efficient and practical group key management scheme dedicated to the mobile cellular networks. This new approach can achieve better performance with less management overhead than other currently available schemes, by the cell-based decentralization of key management functions. Through comparisons with other possible approaches, it is shown that the proposed scheme can obtain much better performance in terms of the communication overhead.