A Cryptographic Key Assignment Scheme for Access Control in Poset Ordered Hierarchies with Enhanced Security

In a hierarchical structure, a user in a security class has access to information items of security classes of lower levels, but not of upper levels. Based upon cryptographic techniques, several schemes have been proposed for solving the problem of access control in hierarchal structures, which are based on only one cryptographic assumption. In this paper, we propose a scheme for access control in hierarchical structures that achieves better security, efficiency, fexibility and generality compared to the schemes previously published.