It has become more and more common to distribute software in forms that retain most or all of the information present in the original source code. An important example is Java bytecode. Since such codes are easy to decompile, they increase the risk of malicious reverse engineering attacks. In this paper we review several techniques for technical protection of software secrets. We will argue that automatic code obfuscation is currently the most viable method for preventing reverse engineering. We then describe the design of a code obfuscator, a tool which converts a program into an equivalent one that is more difficult to understand and reverse engineer. The obfuscator is based on the application of code transformations, in many cases similar to those used by compiler optimizers. We describe a large number of such transformations, classify them, and evaluate them with respect to their potency (To what degree is a human reader confused?), resilience (How well are automatic deobfuscati...

It has become common to distribute software in forms that are isomorphic to the original source code. An important example is Java bytecode. Since such codes are easy to decompile, they increase the risk of malicious reverse engineering attacks. In this paper we describe the design of a Java code obfuscator, a tool which -- through the application of code transformations -- converts a Java program into an equivalent one that is more difficult to reverse engineer. We describe a number of transformations which obfuscate control-flow. Transformations are evaluated with respect to potency (To what degree is a human reader confused ?), resilience (How well are automatic deobfuscation attacks resisted?), cost (How much time/space overhead is added?), and stealth (How well does obfuscated code blend in with the original code?). The resilience of many control-altering transformations rely on the resilience of opaque predicates. These are boolean valued expressions whose values are known to ...

ions and Unstructuring Data Structures Christian Collberg Clark Thomborson Douglas Low Department of Computer Science, The University of Auckland, Private Bag 92019, Auckland, New Zealand. fcollberg,cthombor,dlow001g@cs.auckland.ac.nz Abstract To ensure platform independence, mobile programs are distributed in forms that are isomorphic to the original source code. Such codes are easy to decompile, and hence they increase the risk of malicious reverse engineering attacks. Code obfuscation is one of several techniques which has been proposed to alleviate this situation. An obfuscator is a tool which -- through the application of code transformations -- converts a program into an equivalent one that is more difficult to reverse engineer. In a previous paper [5] we have described the design of a control flow obfuscator for Java. In this paper we extend the design with transformations that obfuscate data structures and abstractions. In particular, we show how to obfuscate classes, arra...