A vehicular ad-hoc network (VANET) is a dynamic model designed to provide communication between vehicles, assisting with problems like traffic management and safe transportation. In a VANET, multicast groups are formed when nearby vehicles have the same application requirements. These multicast groups rely on the confidential sharing of cryptographic group keys, and these keys must change whenever a vehicle joins or leaves the group. An asymmetric lightweight multicast scalable (ALMS) group key management protocol has already been developed by members of the SMILES lab to efficiently manage group keys for VANETs. Our project is to propose a hierarchical version of ALMS in order to improve its scalability for large groups. We will test the effectiveness of this modified protocol via an OMNeT++ simulation, considering the following factors: group key computation time, group key retrieval time, size of encrypted key, and scalability when the number of group members increases.