An Efficient Hierarchical Identity-Based Key-Sharing Method Resistant against Collusion-Attacks

Efficient ID-based key sharing schemes are desired world-widely for secure communications on Internet and other networks. The Key Predistiribution Systems (KPS) are a large class of such key sharing schemes. The remarkable property of KPS is that in order to share the key, a participant should only input its partner’s identifier to its secret KPS-algorithm. Although it has a lot of advantages in terms of efficiency, on the other hand it is vulnerable by certain collusion attacks. While conventional KPS establishes communication links between any pair of entities in a communication system, in many practical communication systems such as broadcasting, not all links are required. In this article, we propose a new version of KPS which is called Hierarchical KPS. In Hierarchical KPS, simply by removing unnecessary communication links, we can significantly increase the collusion threshold. As an example, for a typical security parameter setting the collusion threshold of the Hierarchical KPS i s 16 times higher than that of the conventional KPS while using the same amount of memory at the KPS center. The memory required by the user is even reduced for a factor 1/16 in comparison with the conventional linear scheme. Hence, Hierarchical KPS provides a more efficient method for secure communication.