Reliable Collective Cosigning to Scale Blockchain with Strong Consistency

The HPlane IoT framework abstracts security and privacy concerns of critical IoT infrastructure in a Remote Healthcare Monitoring (RHM) environment. Despite its usefulness, the framework lacks a scalable access control mechanism leading to performance and scalability challenges. Some of these challenges can be overcome by using Byzcoin blockchain that provides strong consistency guarantee. However, we found limitations in Byzcoin with respect to reliability, performance and high failure probability due to the use of unreliable Collective Cosigning (CoSi) protocol. Our practical analysis shows that on an average 10-30% CoSi protocols fail when it uses a spanning tree topology to scale Schnorr multisignature. Thus use of Byzcoin poses a significant risk to critical IoT infrastructure. In this paper, we present a robust spanning tree topology along with an implementation of BLS multisignature. Our enhanced topology successfully tackles reliability limitation while BLS multisignature improves performance and lowers failure probability. This work also summarizes how blockchains can serve as a controller application to provide an effective scalable access control in HPlane IoT framework.