This work proposes a new access control scheme that utilizes a hierarchical key assignment mechanism based on inner product spaces. The scheme brings a lightweight computational load to each entity and is designed to be applicable in a digital medium that implements hierarchical access control policies. By utilizing the method of orthogonal projection and distributing a basis to each group, the scheme enables flexible and efficient left-to-right and top-down policy for any dynamic update or change in the hierarchical structure. The scheme allows a parent group to obtain the secret keys of its child groups, but not the other way around. It is resistant to collusion attacks and privilege creep problems and provides key recovery and indistinguishability property. The scheme has a low storage overhead, and utilizes an efficient key derivation process.