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Summary With the rapid development of technology, digital multimedia has been widely utilized. Access of multimedia contents has become a daily routine. Although multimedia brings ease and convenience for content sharing, it also makes piracy more feasible. For example, it is easy to upload a copyrighted video to YouTube without the owners' permission. Authors and merchants are very much in need of protecting their intellectual property and commercial profits. Digital right management (DRM) systems are provided to fulfill this desire. DRM is a collection of techniques used to control access to copyrighted materials. Because current enterprise DRM solutions are not allowed for customized modification, they cannot fit in our considered scenario perfectly. As a result, we propose a secure DRM system with a design based on user demands, where a consumer can access contents only on authenticated devices until the authorization expires. Our DRM scheme involves a series of robust cryptosystems including AES, SHA-256, and RSA. Applications as DRM agents are implemented on Windows, Mac OS, Android, and iOS platforms. Moreover, we modularized the DRM components for easy extension and integration. For better performance on low-end devices, parameters of encryption are introduced, namely, the key size and the encryption density. We addressed the mask shift problem caused by random access and implemented the device identifier acquirement. The DRM system also proved to have high security and good performance in our analysis. Copyright © 2017 John Wiley & Sons, Ltd.

Accompanied by the widespread deployment of wireless networks, content and service providers are increasingly interested in supporting multicast communications over wireless network. The reliable multicast protocol can provide (assure) efficiency in data delivery carried by the new generation e-services, such as news, advertisement, guiding messages, etc. Its congestion control function enables the transmissions to adapt the sending rate to the available bandwidth and fairly share bandwidth with the widely used transmission control protocol (TCP) traffic in the networks. Many e-services can be brought and built on the reliable multicast congestion control protocols to the roaming mobile subscribers. However, the reliable multicast congestion control protocols are affected by the wireless packet losses, resulting in degraded multicast performance. This article presents PGMCCW, a pragmatic general multicast congestion control protocol for wireless networks. PGMCCW can differentiate the wireless losses as well as the congestion losses on multicast and can also elect the proper group representative from the multiple receivers in the different wireless sub-networks. The simulation results validate that this scheme is effective to alleviate the influence of the wireless losses and improve the performance over wireless networks. Copyright © 2005 John Wiley & Sons, Ltd.

An ad hoc network is formed by a collection of mobile nodes without any centralized access point or existing infrastructure. Communications between mobile nodes require routing over multiple-hop wireless paths. Since mobile nodes could be of high mobility, an effective and adaptive routing protocol must have ongoing details of the topology information. However, it wastes limited bandwidth to keep routing information up-to-date and reliable. Thus, one of the crucial design objectives to achieve routing responsiveness and updating efficiency is the minimization of reaction to mobility. Specifically, a scalable and QoS-guaranteed routing protocol is desired for novel multimedia applications in mobile ad hoc networks. In this paper, we propose an efficiently repairable routing protocol, called Gravitational Cluster Routing (GCR) Protocol. It contains a stable cluster structure to cover dense areas and avoid articulation nodes. The reaction to mobility can be reduced significantly by unicast. Active routing paths can be maintained locally in each cluster. Besides, repairable levels of active routing paths, which rank their stabilities, are evaluated. By their aid, the proposed GCR can find routing paths that satisfy different parameters of QoS. These mechanisms can improve the stability of active connections. Copyright © 2003 John Wiley & Sons, Ltd.