SRST: A secure and resilient synchronization of time for WSNs in IoT applications

Abstract

Many applications of Wireless Sensor Networks (WSNs) in internet of things require accurate time synchronization for the successful realization. In a hostile environment, protecting time synchronization against faulty timestamps injection attacks is paramount. Malicious nodes (MNs) could broadcast faulty timestamps to decrease the accuracy of the whole network. The Receiver-Only (RO)-based synchronization methodology achieves high accuracy while reducing the number of timing messages compared to other methodologies. However, RO is vulnerable to node failure and supports only a single reference, which makes it inaccurate in the presence of MNs. To address these limitations, we propose SRST, a secure and resilient synchronization of time for WSNs. SRST employs a novel time synchronization model that extends RO to allow synchronizing sensor nodes to multiple mutually-synchronized references, which enhances robustness against node failure and malicious behavior. SRST optimizes convergence time by synchronizing the RO node with its synchronized 1-hop and 2-hop neighbors. RO node applies a new delay threshold-based detection technique to identify reference nodes as MNs through detection of faulty timestamps. SRST is topology-independent and can be applied to multi-tier, cluster-based and flat topologies. We validated SRST through simulations and prototype experiments, comparing its performance with several state-of-the-art protocols. The results demonstrate that SRST outperforms existing protocols in accuracy, achieving synchronization within less than $1\mu s$, and accelerates convergence time by a factor of 31.25 compared to the best-known protocol. SRST has also been shown to be more effective in mitigating faulty timestamp injection attacks, successfully detecting errors of $6\mu s$ with a 100% success rate and ensuring that the clocks of any two nodes do not deviate by more than $6\mu s$. Furthermore, the results indicate that SRST imposes little communication overhead.