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Code virtualization built upon virtual machine (VM) technologies is emerging as a viable method for implementing code obfuscation to protect programs against unauthorized analysis. State-of-the-art VM-based protection approaches use a fixed scheduling structure where the program follows a single, static execution path for the same input. Such approaches, however, are vulnerable to certain scenarios where the attacker can reuse knowledge extracted from previously seen software to crack applications using similar protection schemes. This paper presents DSVMP, a novel VM-based code obfuscation approach for software protection. DSVMP brings together two techniques to provide stronger code protection than prior VM-based schemes. Firstly, it uses a dynamic instruction scheduler to randomly direct the program to execute different paths without violating the correctness across different runs. By randomly choosing the program execution paths, the application exposes diverse behavior, making it much more difficult for an attacker to reuse the knowledge collected from previous runs or similar applications to perform attacks. Secondly, it employs multiple VMs to further obfuscate the relationship between VM bytecode and their interpreters, making code analysis even harder. We have implemented DSVMP in a prototype system and evaluated it using a set of widely used applications. Experimental results show that DSVMP provides stronger protection with comparable runtime overhead and code size when compared to two commercial VMbased code obfuscation tools.

Unauthorized code modification based on reverse engineering is a serious threat for software industry. Virtual machine based code obfuscation is emerging as a powerful technique for software protection. However, the current code obfuscation techniques are vulnerable under semantic attacks which use dynamic profiling to transform an obfuscated program to construct a simpler program that is functionally equivalent to the obfuscated program but easier to analyze. This paper presents DSA-VMP, a novel VM-based code obfuscation technique, to address the issue of semantic attacks. Our design goal is to exploit dynamic data flows to increase the diversity of the program behaviour. Doing so can reduce the effectiveness of dynamic profiling. Our approach using multiple bytecode handlers to interpret a single bytecode and hiding the logics that determine the program execution path (it is difficult for the attacker anticipate the program execution flow). These two techniques greatly increase the diversity of the program execution where the protected code regions exhibit a complex data flow across multiple runs, making it harder and more time consuming to trace the program execution through profiling. Our approach is evaluated using a set of real-world applications. Experimental results show that DSA-VMP can well protect software against semantic attacks at the cost of little extra runtime overhead when compared to two commercial VM-based code obfuscation tools.