A Hierarchical Key Assignment Scheme

This work introduces a novel access control scheme employing a hierarchical key assignment mechanism based on inner product spaces. The scheme is computationally lightweight and designed for digital environments with hierarchical access control policies. By leveraging orthogonal projection and distributing a basis to each group, it supports flexible and efficient left-to-right and top-down policies, accommodating dynamic updates in the hierarchy. The scheme allows parent groups to derive the secret keys of their child groups while preventing the reverse. It ensures resistance to collusion attacks and privilege creep, offering key recovery and indistinguishability properties. With low storage overhead and an efficient key derivation process, the scheme provides a practical solution for secure hierarchical access control.