Evaluation of Dual-Structure Key-management Scheme Suitable for Mobile Services

Copyright protection is a major issue in online content distribution services and many key-management schemes have been proposed for protecting content. Tree-based schemes aim at reducing the load on the server, and do not give consideration to that on clients. This scheme is not fully suitable for devices with low computational capacity. On the other hand, the load on clients is low in a star-based scheme. However, the load on the server becomes large in proportion to the number of clients. This structure is far from scalable. We propose a key-management scheme that is the intermediate scheme of a star-based scheme and a tree-based scheme. Then, we evaluate both the load on the server and clients in key-management scheme using the three structures. We find that the load on server and that on clients in our scheme have a relation of trade-off. We can construct optimal key-management structure satisfying system requirements using our scheme. Furthermore, the loads on both the server and clients in our scheme are lower than tree-based structure scheme under a certain condition.