An improved RSA-based access control scheme for hierarchical groups

We reveal some drawbacks in Ghodosi´s scheme and present an improved RSA-based access control scheme for hierarchical groups. The proposed scheme enjoys the following properties: 1. The size of an individual´s share sequence is bounded by a small constant times the size of the RSA modulus corresponding to that group. 2. The delegation of information flow from higher-level groups to lower-level groups is completely non-interactive. 3. It doesn´t require an online trusted authority to upgrade the system as soon as communication happened. 4. The proposed scheme is resistant to conspiracy.