CBP: Coalitional-Game-Based Broadcast Proxy Re-Encryption in IoT

This article proposes coalitional game-based broadcast proxy re-encryption (P-RE) in IoT—a broadcast P-RE for adding new IoT devices. The P-RE is extended to broadcast P-RE to prevent recalculation of the re-encryption key (ReKey). However, the group of recipients needs to be predetermined before the calculation of the ReKey. If any new IoT device requires the same data, an individual ReKey is generated for him/her. Hence, generating individual ReKey is an overhead for the organization. We propose a ReKey updation for the broadcast P-RE method. If excessive IoT devices want to join the group of the existing recipient, then updation needs to be done learnedly as an excessive number of recipients in a group increases the computation cost of the decryption extremely for all the members of the group. Therefore, we use the coalitional game theory to estimate the optimal number of new recipients from all new recipients. We update the ReKey for the optimal number of members and a separate ReKey is calculated for other recipients. We prove the correctness of the CBP. We prove that if any recipient behaves maliciously, s/he cannot get the secret key of the organization.