Malicious cryptography techniques for unreversable (malicious or not) binaries

Abstract. Fighting against computer malware require a mandatory step of reverse engineering. As soon as the code has been disassemblied/de-compiled (including a dynamic analysis step), there is a hope to un-derstand what the malware actually does and to implement a detection mean. This also applies to protection of software whenever one wishes to analyze them. In this paper, we show how to amour code in such a way that reserse engineering techniques (static and dymanic) are absolutely impossible by combining malicious cryptography techniques developped in our laboratory and new types of programming (k-ary codes). Suitable encryption algorithms combined with new cryptanalytic approaches to ease the protection of (malicious or not) binaries, enable to provide both total code armouring and large scale polymorphic features at the same time. A simple 400 Kb of executable code enables to produce a binary code and around 2140 mutated forms natively while going far beyond the old concept of decryptor.