Fast and Secure Group Key Dissemination Scheme for Out-of-Range V2I Communication

In vehicular communications, a group key that is only shared by the group subscribers is widely used for encrypting or signing multicast messages. A major issue with the group key is how to efficiently and securely transmit an updated group key for which numerous research results have been published. However, in the existing schemes, because vehicles receive the group key only from roadside units (RSUs), vehicles that are out of communication range cannot receive the updated group key. In this case, those vehicles can receive no data nor participate in group communication until they get the newest group key from the RSU. To overcome the aforementioned out-of-range limitation, we propose a new group key delivery scheme based on vehicle-to-vehicle (V2V) communication. The proposed scheme enables the vehicle in a group out of the communication range of the RSU to receive the group key from other vehicles in the same group. Two main parts of the scheme are a vehicle-verification protocol and a group-key-verification protocol. With the first protocol, a group key sender can verify if the vehicle that tries to receive the group key is a group member, and with the second protocol, the group key receiver can check the integrity of the group key. The two protocols include no interaction with a third party and, moreover, do not use any unencrypted privacy-sensitive information within a vehicle. By using mathematical analysis, we theoretically demonstrate that our scheme is safe against possible attacks. In addition, by using simulations, we show that the V2V group key delivery scheme guarantees faster group key dissemination than the existing schemes.