Resource-aware broadcast encryption for selective-sharing in mobile social sensing

The rapid proliferation of smartphones has led to the emergence of mobile social sensing applications, spanning sharing of health data, location-based encounters, and transportation. A major concern for such applications is selective sharing, i.e., how does a user publish a sensor data stream confidentially to only authorized members in his/her social network? The needs of mobile sensing applications, such as dynamic communities and data dissemination from resource-constrained handhelds, make this problem more challenging than apparent. The novelty of this paper lies in the use of a cryptographic scheme called broadcast encryption to enable selective sharing for mobile social sensing. This is in contrast to unicast or pairwise encryption that is commonly used today. We evaluate state-of-art broadcast encryption schemes and note that they provide either efficiency, or adaptation to dynamic group sizes, but not both. We propose ECS (Extended Complete Subtree), a resource-aware broadcast encryption scheme that can efficiently support dynamic groups. We implement each encryption scheme on the Nokia N800 handheld device and demonstrate that ECS is more feasible than other schemes in terms of key storage, code size, and encryption and decryption efficiency.