Modified cryptographic key assignment scheme for a group-oriented user hierarchy

A modified cryptographic key assignment scheme for the dynamic access control in a group-oriented user hierarchy is presented. In the partially ordered set (poset, for short) user hierarchy (G(j) less than or equal to G(i)) embedded in a group-oriented (t, n) threshold cryptosystem, the source group G(i) has higher security clearance to access the information items held in the target group G(j). If a target group G(j) has multiple paths reachable from a source group G(i), we must choose the least cost path to rapidly resolve the dynamic access control problem. Furthermore, multiple threshold values are also considered in order to meet the different security requirements.