Key Management Schemes for Multilayer and Multiple Simultaneous Secure Group Communication

Many emerging applications are based on group communication model and many group communications like multimedia distribution and military applications require a security infrastructure that provides multiple levels of access control for group members. The group members are divided into a number of subgroups and placed at different privilege levels based on certain criteria. A member at higher level must be capable of accessing communication in its own level as well as its descendant lower levels but not vice versa. In this paper we propose a key management scheme for this multilayer group communication. We achieve substantial reduction in storage and encryption cost compared to the scheme proposed by Dexter et al. We also address periodic group rekeying. Applications like scientific discussion and project management may lead to a scenario in which it is necessary to set up multiple secure groups simultaneously, and few members may be part of several secure groups. Managing group keys for simultaneous secure groups is critical. In this paper we propose a novel key management scheme for multiple simultaneous groups. 1. Introduction Many emerging applications like secure audio and visual broadcasts, pay-per-view, scientific discussion, and teleconferencing are based on group communication model. Several users participate in these applications, and multicast communication is an efficient means of distributing data to a large group of participants [1–3] since it reduces the demands on network and bandwidth resources. But, the communication among these participants must be carried out confidentially. Thus, a common key known as group key or secret key must be established with all the users in the group, so that any group member can encrypt the message using this key, and all others can decrypt the message using the same key. The group, being dynamic in nature, allows member join and leave events. Efficiently managing group key for large, dynamically changing groups is a difficult problem. Every time when a new member joins the group, the group key must be changed in order to provide backward access control (i.e., new members should not be able to access past communication). Similarly, when a user leaves the group, the group key must be changed so that leaving member cannot have access to future communication that takes place between remaining group members, known as forward access control. This group key updating process is referred to as rekeying. Rekeying process involves changing the group key whenever there is a membership change and distributing it among