The purpose of this research is to propose a new theoretical model for access control in a hierarchy. The main point is that the superiors in an organization only need to possess a secret key. And, through a simple computation, the superiors can know any secret key of his (or her) subordinates, i.e., the superiors need not know every subordinate's secret key in advance. Our scheme has the following advantages: (1) .reduce the burden of managers on secret key management: (2) .preserve the feature of sharing secret data; and (3) .the effect of data security works well.