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Wireless sensor networks are a significant subfield of distributed systems, and a large number of their applications require time synchronization. Sensor nodes are powered by batteries. In order to reduce the interference of the peripheral environment on the node as much as possible, the size of the node is relatively small and the circuit design, storage, and calculation are relatively simple. Therefore, wireless sensor network nodes have limited energy, low computing power, and low communication capacity. In addition, the clock of the wireless sensor network node is usually realized through the local crystal oscillator and CPU interrupt mechanism, which is obviously affected by manufacturing errors, temperature changes, and CPU processing delays. Therefore, this research reviews and analyzes the development and current situation of time synchronization and puts forward the challenges faced by time synchronization-related research institutes. From the perspective of dynamic cybernetics, the feasibility of optimization based on Kalman filtering is analyzed. Finally, the article describes the system modeling process, including the clock model and the state equation and observation equation of Kalman filter and uses Matlab platform to carry out experimental simulation and analysis on the precise time synchronization protocol based on Kalman filter in the wireless sensor network environment.

Since digital forensics becomes more and more popular, more and more attention has been paid to the originality and validity of data, and data preservation technology emerges as the times require. However, the current data preservation models and technologies are only the combination of cryptography technology, and there is a risk of being attacked and cracked. And in the process of data preservation, human participation is also needed, which may lead to data tampering. To solve problems given, this paper presents a data preservation model based on blockchain and multidimensional hash. With the decentralization and smart contract characteristics of blockchain, data can be automatically preserved without human participation to form a branch chain of custody in the unit of case, and blockchain has good antiattack performance, which is the so-called 51% attack. Meanwhile, in order to solve the problem of data confusion and hard to query caused by the excessive number of cases, hash, cryptography, and timestamps are used to form a serialized main chain of custody. Because of the confliction problem of hash and judicial trial needs to absolutely guarantee the authenticity and validity of data, multidimensional hash is used to replace regular hash. In this way, the data preservation becomes an automatic, nonhuman-interventional process. Experiments have been carried out to show the security and effectiveness of the proposed model.

Time synchronization of clocks in the sensor nodes for wireless sensor networks (WSNs) is a fundamental technology for most mission-critical applications. Most of past research in time synchronization for WSNs, however, has only focused on achieving some of the goals at a time, such as accuracy, energy consumption, completion time, etc., making these solutions less capable of adapting to different application requirements. In this paper, we propose a new time synchronization algorithm named MBATS (mobile beacon-based adaptive time synchronization) in which a mobile beacon is employed to move or fly over the sensor deployment area to complete time synchronization. Moreover, MBATS is designed so that the number of sensor nodes that are synchronized by one instance of time synchronization from the mobile beacon could vary dynamically to meet application requirements on accuracy, completion time and energy consumption, making the proposed MBATS algorithm highly adaptable to different application requirements. In addition to showing the advantage of the proposed MBATS algorithm on the adaptability of time synchronization as well as on some of the main metrics of synchronization over comparable schemes for WSNs, we also present the results of our study on comparing the performance of letting the mobile beacon traverse along a designing path versus follow a random path. Such a study is important since it would allow us to learn the performance gains that we can expect to achieve with extra control effort spent on designing the path over the effortless random path strategy. Such study could provide us with some clues on how to choose a suitable time synchronization strategy to better meet application requirements, which may not necessarily be the designed path strategy due to the tradeoff between cost and performance gains.

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