Dynamic contributory key management based on Weighted-Join-Exit-Tree

Time efficiency in key establishment and update is one of the major problems contributory key managements strive to improve. In this paper, we present a contributory group key management based on weighted-join-exit-tree and named as WJT to get better time efficiency in key update. Built upon tree-based group key management, WJT has three improvements, the first is the join algorithm to inserting the new user at the root of the join tree, the second is the exit tree structure organized as a weighted tree according to userspsila leaving time, and the last is the tree balancing algorithm to minimize the main tree height. Theoretical analysis shows that the asymptotic average join time and leave time of WJT are reduced to O(1) from previous O(log(log n)), where n is the group size. Simulations and comparisons with existing key managements demonstrate that WJT is efficient in group key establishment and update.