On Achieving Reliable and Efficient Precondition Execution Enforcement in Internet-of-Things

In IoT it is common that before a command can execute on a smart object, certain preconditions (on possibly other objects) should be met first to ensure safety or efficiency. Existing work has realized automatic precondition execution: when a user issues a command, her device automatically finds out all the precondition commands, and executes them in the correct order. However, security issues have not been considered: it assumes that a user device honestly follows the order it has been told to send commands to objects, and objects trust users thus do not check whether the preconditions are indeed met. In this paper we propose two strategies to enforce precondition execution order: 1) Snowball relying on signed declarations from precondition objects; 2) Onion using disposable access tokens encrypted by a trustworthy server. Our extensive analysis and experiments on a 20-node testbed show that both strategies are secure and reliable. Snowball has higher availability while Onion is more efficient and responsive: Onion uses 1.6/2.1 s to access 20 one-hop/multi-hop objects, 62%/54% of Snowball's time.