An Efficient Key Assignment Scheme Based on One-Way Hash Function in a User Hierarchy

In order to solve the problems resulted from dynamic access control ina user hierarchy, a cryptographic key assignment scheme is proposed byProf. Lin to promote the performing ability and to simplify theprocedure. However, it may cause the security in danger as the userchanges his secret key; besides, some secret keys may be disclosed dueto the unsuitable selection of the security classes' identities.Through setting up a one-way hash function onto Lin's scheme, theproposed modification can greatly improve the security of Lin's scheme.