Study the Logic Invariability in Subroutine's Junk Code Fuzzy Transformation

Junk code fuzzy transformation (JCFT) is one of the effective approaches of the code obfuscation technology. Based on the analysis of current junk code strategies, this paper presents a new method named junk code encryption algorithm of subroutine, and depicts the algorithm with formalized language. The paper studies how to prove the logic invariability of subroutine’s JCFT with formalized method. After studying the formalized definition of subroutine’s JCFT, some lemmas are extracted. With these lemmas, and from three aspects such as "XOR and CMP Expansion", "False Embranchment Construction" and "JNE Append Junk Code", the paper proves that the procedure which transforms with subroutine’s JCFT has the same logicality with the original procedure.