DIVILAR: diversifying intermediate language for anti-repackaging on android platform.

App repackaging remains a serious threat to the emerging mobile app ecosystem. Previous solutions have mostly focused on the postmortem detection of repackaged apps by measuring similarity among apps. In this paper, we propose DIVILAR, a virtualization-based protection scheme to enable self-defense of Android apps against app repackaging. Specifically, it re-encodes an Android app in a diversified virtual instruction set and uses a specialized execute engine for these virtual instructions to run the protected app. However, this extra layer of execution may cause significant performance overhead, rendering the solution unacceptable for daily use. To address this challenge, we leverage a light-weight hooking mechanism to hook into Dalvik VM, the execution engine for Dalvik bytecode, and piggy-back the decoding of virtual instructions to that of Dalvik bytecode. By compositing virtual and Dalvik instruction execution, we can effectively eliminate this extra layer of execution and significantly reduce the performance overhead. We have implemented a prototype of DIVILAR. Our evaluation shows that DIVILAR is resilient against existing static and dynamic analysis, including these specific to VM-based protection. Further performance evaluation demonstrates its efficiency for daily use (an average of 16.2 and 8.9 increase to the start time and run time, respectively).