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During the rapid development of mobile wireless technologies and applications, the Android operating system, due to its open-source characteristics, has become the most popular development platform in the smartphone market. Meanwhile, as Android-based intelligent mobiles devices experience a rapid increase in numbers, high-tech crimes involving such devices have become more versatile, affecting an ever increasing amount of data, thus making digital evidence an indispensable part of the evidence that needs to be seriously dealt with during crime investigations. Consequently, understanding the internal structure of Android and the various data operations in the file systems becomes necessary in Android-based digital forensics. In this paper, we survey the state-of-the-art of technologies in Android-based digital forensics and some popular tools in the aspects of data recovery and acquisition, file system analysis and data analysis. We also discuss some technical challenges and point out future research directions in Android-based digital forensics.

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.

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