Generalization of multicast encryption for Internet of Things deployment

The problem of multicast encryption has been a focus of attention in the Internet of Things environment for the last decade, in which one central server generates and securely distributes a common key designated for a group of IoT devices. These devices can establish secure communication by sending encrypted content within the group using the earlier established group key. It is crucial that the encrypted content can be decrypted only by the member devices. An issue arises when the number of multicast groups increases, and devices tend to be part of various groups simultaneously. Hence we consider a generalization of multicast encryption where multiple multicast groups exist in the IoT environment that are not independent. That means the involvement of an IoT device is not restricted to only one group, which was the case earlier. In our study, the parameters of interest are computational overhead per device, the number of keys stored, and the bandwidth required per transmission as a function of the total number of devices d and the number of groups m. As our main result, we considered two cases in framing efficient and secure solutions for the generalization of multicast encryption. Since several solutions are already proposed for simple multicast encryption techniques, first is the case where it is assumed that a prior optimal solution is already known for multicast encryption and how to build a multi-group scenario out of this. Second, if this situation is not there, we need to define the generalized problem for multicast encryption, which includes overlapped multiple multicast groups. Henceforth, this paper defines important security theorems and their proofs for both cases, along with security models and strong security definitions.