Algorithms for dynamic multicast key distribution trees

Abstract

Many secure group communication systems rely on a group key, which is a secret shared among the members of the group. Secure messages are sent to the group by encrypting them with the group key. Because group membership is dynamic, it becomes necessary to change the group key in an efficient and secure fashion when members join or leave the group. We present a series of algorithms for solving this problem based on 2-3 trees, where each internal node has degree 2 or 3. The algorithms a t t e m p t to minimize the worst case communication cost of updating the group key and the auxiliary keys needed by the algorithms. The algorithms are analyzed for the worst case performance and evaluated empirically via simulations. We focus on the trade-off between the communication cost due to the structure of the tree and that due to the restructuring of the tree to maintain its structure.

Energy and Bandwidth-Efficient Key Distribution in Wireless Ad Hoc Networks: A Cross-Layer Approach

“…That is, the number of GC transmissions is proportional to w a (M 1 ). In fact, it has been shown that GC transmissions due to member deletions increase as a function of d log d N [8], [16], [20]. The cost of join operations on the other hand, is proportional to the depth of the leaf the new user is assigned, a function of log d N [8], [16], [20].…”

“…Finding a solution to (8) implies finding an optimal allocation of members to leaf nodes, so that the sum of energy costs to multicast to subgroups that share common keys is minimized. To our knowledge, there is no algorithm that yields an optimal key tree, or a characterization of the complexity of the problem in (8).…”

License Protection with a Tamper-Resistant Token

“…This is a mechanism that has been used in secure group communication for key distribution and management [11]. Figure 4 provides an example of a key tree.…”

Distributed Construction of a Fault-Tolerant Network from a Tree

“…An MDwalk stepping on a node that is not an expander node implies that there might be a non-negligible fraction of such nodes in the tree. Hence, in this case the MDwalk is interrupted (lines 11 and 12) and a special request BIrequest is deterministically sent to the root that results in a BIwalk (lines [19][20][21][22]. When the tree is large, there are more nodes in the path to the root and thus a higher probability of starting an MDwalk (lines [7][8][9][10].…”

“…Their acyclic structure allows the use of simple protocols for data sharing and coordination, e.g., key management [19,29], hierarchical peer-to-peer systems [15] and distributed mutual exclusion protocols [37,9,20,44,34]. Moreover the hierarchical nature of trees maps directly to many real world applications, e.g., the Domain Name System [33], distributed certification authorities [25] and distributed directory protocols [11].…”