Protecting android apps against reverse engineering by the use of the native code

Abstract

Having about 80% of the market share, Android is currently the clearly dominating platform for mobile devices. Application theft and repackaging remains a major threat and a cause of significant losses, affecting as much as 97% of popular paid apps. The ease of decompilation and reverse engineering of high-level bytecode, in contrast to native binary code, is considered one of the main reasons for the high piracy rate. In this paper, we address this problem by proposing four static obfuscation techniques: native opaque predicates, native control flow flattening, native function indirection, and native field access indirection. These techniques provide a simple and yet effective way of reducing the task of bytecode reverse engineering to the much harder task of reverse engineering native code. For this purpose, native function calls are injected into an app’s bytecode, introducing artificial dependencies between the two execution domains. The adversary is forced to analyze the native code in order to be able to comprehend the overall app’s functionality and to successfully launch static and dynamic analyses. Our evaluation results of the proposed protection methods witness an acceptable cost in terms of execution time and application size, while significantly complicating the reverse-engineering process.