The Techniques Research Of The Code Obfuscation Based On Control Flow Transformation

In recent years, along with the computer software playing a crucial role in variousareas, software protection technology has been more and more attention. Because ofsoftware crackers could use reverse engineering technology to attack code by static analysisand dynamic tracking etc, so in order to guarantee the safety and reliability of software,must take effective software protection scheme. Among the many software protectiontechnologies, code obfuscation technology through code obfuscation transformation,improving anti-attack capability of software, protecting the code from software crackers, italso has a good confounding effect and easy to implement and low development costs.This thesis mainly aims at researching the control flow obfuscation of the codeobfuscation technology, in order to guarantee the software code obfuscation strength enoughto resist attacks, and solve the problem of static authorization of software registrationverification mechanism, proposed a code control flow obfuscation method based on sharingtechnology. The main work is as follows:Firstly, briefly introduced the software reverse engineering technology and codeobfuscation technology, including static analysis, dynamic analysis, research status of codeobfuscation, definition, classification and effectiveness evaluation. Specifically studied thecode control flow obfuscation transformation, deep analyzed the five methods which the useof garbage code, using opaque predicates, inserting extra control flow, planishing controlflow structure, extending branches jump.Secondly, elaborated the sharing principles, proposed a code control flow obfuscationmethod based on sharing technology. Primarily divided the secret key into many segmentsin software registration authentication mechanisms to construct a number of mutuallydifferent validation functions, then combined with the opaque predicates and branching functions in conventional control flow obfuscation methods, finally plugged them into thesoftware code, on the one hand confused control flow structure of the program, on the otherhand dynamically validated the user’s illegal operation.Then, briefly introduced the relative knowledge of game theory, made theprotection-attack relationship of developers and crackers in software protection abstract intoa defensive attack-attack game behavior, established a software protection game modelbased on the strategy of sharing. Analyzed the attacked complexity which the crackedsoftware needed, and used the model to validate the correctness of control flow obfuscationmethod based on sharing technology in theoretical methods.Finally, detailedly analyzed four aspects of performance such as obfuscation strength,anti-attack capability, overhead, concealment after using improved method to confuse thecode, the experiments verified the effectiveness of the code control flow obfuscationmethod based on sharing technology.