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Reverse engineering, repackaging and misuse of Android apps are becoming more and more widespread. Many obfuscation schemes are not enough against sustainably evolving reverse engineering techniques, while others have performance problems or limitations. In this paper, we propose a novel scheme that redirects method invocation dynamically to hide the actual control flow of the program. Firstly, some pivotal methods are replaced by others unrelated methods, so that the actual semantics of the program no longer appear. Then by modifying the entry address of the methods in the obfuscated code, the methods execution automatically jumps to the corresponding target methods without any code modification. In order to accurately restore the control flow, the encrypted mapping is decrypted using dynamic passwords from the server in the standalone Java interpreter. Since the obfuscated program semantics and program execution results can not be significantly different, it is almost impossible to reveal the real logic of the program through static analysis. The scheme can also effectively increase the difficulty of dynamic analysis. The evaluation results show that the semantic redirection obfuscation scheme can well hide the actual control flow of the program and both the time and space consumption introduced are acceptable.

As the applications on smartphones and tablets are getting richer and more powerful, people are more willing to do their daily works and entertainments on mobile devices. Sharing and collaborating on these devices in a convenient and safe way has become a growing demand in modern life. However, due to the lack of a flexible access control strategy of the official online services, typical applications such as email, video and music do not support this kind of sharing scheme. In this paper, we propose TrustyShare to provide a general sharing solution based on the ARM TrustZone technology which has a extremely wide range of applications in mobile terminal devices and Internet of Things devices. Our solution allows users to share services they enjoy without the official support from these services, while avoiding the disclosure of their private credentials. In addition, credential owners have full control on how and when others can use their services through flexible access control policies. We implement our solution on OP-TEE platform, and our experimental results demonstrate that TrustyShare works well with good performance.

WireGuard, a novel VPN proposed in 2017, has been widely accepted in the industry, since it is simpler, leaner and more efficient than traditional VPNs. However, WireGuard ignores the risks of key stolen and abused on both desktop and mobile platform. These vulnerabilities might be utilized by attackers to sneak into the protected network through VPN tunnel provided by WireGuard easily without permission. It is especially obvious on mobile platforms, since they are mostly online all day and the attack scenarios are more complicated and changeable. In this paper, we propose an enhanced WireGuard Android version called SeWG based on TEE. We use TEE (Trusted Execution Environment) technology to achieve secure key storage, preventing the misuse of the private key. And we design corresponding dynamic authentication mechanisms for user mode and kernel mode respectively, to prevent malware from sneaking into the secure tunnel. Finally, we implement SeWg scheme on QSEE, the TEE platform developed by Qualcomm. Our experimental results demonstrate that SeWG can work well with high efficiency.

Taxi plays an important role in public transportation. However, in real life, it usually takes a long time for passengers to wait for an unoccupied taxi, while number of no-load taxi is very high. Optimized scheme is required to handle global taxi dispatching. The paper presents a novel method of taxi dispatching based on Artificial Fish Swarm Algorithm (AFSA). To avoid slow convergence and falling into local optimum, standard AFSA is improved using strategies of optimizing visual range, step size and swimming behavior. We compare our improved algorithm with standard AFSA and Particle Swarm Optimization through the evaluation with real data of GPS trajectory of 12,000 taxis in Beijing and make performance analysis of effects of parameter configuration to dispatching algorithm. The experimental results show good effectiveness of our method.