This report contains a discussion of the difficult problem of key management for multicast communication sessions. It focuses on two main areas of concern with respect to key management, which are, initializing the multicast group with a common net key and rekeying the multicast group. A rekey may be necessary upon the compromise of a user or for other reasons (e.g., periodic rekey). In particular, this report identifies a technique which allows for secure compromise recovery, while also being robust against collusion of excluded users. This is one important feature of multicast key management which has not been addressed in detail by most other multicast key management proposals [1,2,4]. The benefits of this proposed technique are that it minimizes the number of transmissions required to rekey the multicast group and it imposes minimal storage requirements on the multicast group.

In this paper, we describe a novel approach to scalable group re-keying for secure multicast.

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We study the stability of the dynamics of a deterministic model of Transmission Control Protocol (TCP) traffic in a multiple flow, multiple router data network. In this model, flow rates increase continuously until network congestion causes them to decrease discontinuously. In computer simulations of small networks, trajectories appear to approach periodic orbits for most but not all parameter values. We prove that if all the data flows are coupled, periodic orbits must be exponentially attracting and thus persist under parameter changes, regardless of network size. Furthermore, we describe the model as a discontinuous but piecewise affine map and show that trajectories must either approach a periodic orbit or come arbitrarily close to map discontinuities.