Centralized vs. Decentralized Group Key Management Sample Clauses

Centralized vs. Decentralized Group Key Management. In this subsection, we compare the performance of our interval-based algorithms and a centralized key management approach. We consider the centralized logical key tree (LKT) ap- proach [13] upon which our Batch algorithm is developed (see Section III-B). Similar to the interval-based algorithms, we assume that the key tree in the LKT approach is a binary tree and that the keys of the tree nodes are computed based on the TGDH protocol [11]. Among the group members, we select a group controller that centrally renews the group key at periodic rekeying intervals. We assume that the group controller knows the keys of all the nodes in the key tree and that a newly joining member sends its individual secret key to the group controller via a secure channel. At the beginning of a rekeying interval, the group controller first rekeys all (non-leaf) renewed nodes using the TGDH protocol. It then encrypts the updated secret key of each renewed node with the respective secret keys of the two child nodes via any symmetric encryption algorithm. Afterward, it broadcasts the encrypted keys to the group. Every member, upon receiving the encrypted keys, decrypts the keys along its key path with the secret keys it holds. } { We use Fig. 7 to illustrate the LKT approach. Suppose that M1 is the group controller. It first rekeys all renewed nodes as in the TGDH protocol. It then broadcasts to the group the following encrypted keys: (K0)1, (K0)2, (K1)3, (K1)4, (K2)5, (K2)6, (K5)11, (K5)12 , where (Ki)j refers to the secret key Ki of parent node i encrypted by the secret key Kj of the child node j. For example, in order for member M3 to obtain the group key K0, it first decrypts (K1)4 with K4, followed by (K0)1 with K1. We assume that the group controller broadcasts the en- crypted keys using the view-synchronous communication model as in the interval-based algorithms. While the group controller can broadcast the encrypted keys via the point-to- multipoint multicast, such a communication model has two limitations. First, if the underlying group communication is multipoint-to-multipoint-based such that every member can be a sender, setting up an extra multicast channel will be an overhead. Also, it is possible for the group controller to leave the group. All other members have to detect the group controller’s departure and install a new membership view in order to select another group controller. The group controller’s departure, however, cannot be detected with the unilateral point...