Exploiting Power Grid for Accurate and Secure Clock Synchronization in Industrial IoT

Abstract

Desynchronized clocks among nodes in industrial Internet of Things (IoT) can degrade system performance and even lead to safety incidents. Clock synchronization protocols based on network message exchanges, though widely used in current industrial systems, are susceptible to delay attacks against the packet transmission. This vulnerability cannot be solved by conventional security measures such as encryption, and remains an open problem. This paper proposes to use the sine voltage waveform of a utility power grid to synchronize "things" connected to the same grid. Our experiments demonstrate that minute fluctuations of the voltage's cycle length encode fine-grained global time information in a city-scale utility grid. Based on this key result, we develop a clock synchronization approach that achieves sub-ms accuracy and is provably secure against packet delay attacks. Implementation results show that our approach achieves an average synchronization error of 0.1 ms between two IoT nodes that are 10 km apart. When the proposed system is deployed within the same floor of a building, the error reduces to 10 us.