Research On The Code Protection Technology Of Android System

With the rapid development of smart mobile phone, the popularization rate of the Android system is getting higher and higher. The attendant problem is the Android code protection. Many malicious programs will use repackaging technology to be implanted into the common application, and achieve its purpose of destruction. This paper will present a code reinforcement process which is based on the research of Android system security mechanisms and code protection method, so as to protect the safety of the code.This paper firstly studies the code development mode in Android application layer and the characteristics of five major components, and then discussed the three basic Android security mechanisms---sandbox mechanism, permission mechanism and signature mechanism. Combined with the reverse engineering technology of Android, this paper also proposed the code protection method in six aspects, including integrity checking, code obfuscation, dynamic loading, NDK development, antireverse, anti-debugging and information storage on network. Then this paper combines with these code protection methods and presents a code reinforcement process based on Android reverse engineering.The reinforcement process includes these steps: reversing, analysis of sensitive permissions and functions, packaging and replacing of functions, importing encryption so library, implantation of checking code and anti-debugging code, code obfuscation. Through multi-level code reinforcement method, it can take good protection in the aspects of anti-tamper, anti-reverse, anti-crack and so on.Finally, according to the reinforcement process, this paper does an experiment on a sample program. By comparing the experimental process and the experimental results before and after, we can find this method can protect the code security of Android application in a certain degree. By these results, this paper also proposed the following research content and the modification direction.