Anti-disassembly using Cryptographic Hash Functions

Computer viruses sometimes employ coding techniques intended to make analysis difficult for anti-virus researchers; techniques to obscure code to impair static code analysis are called anti-disassembly techniques. We present a new method of anti-disassembly based on cryptographic hash functions which is portable, hard to analyze, and can be used to target particular computers or users. Furthermore, the obscured code is not available in any analyzable form, even an encrypted form, until it successfully runs. The method’s viability has been empirically confirmed. We look at possible countermeasures for the basic anti-disassembly scheme, as well as variants scaled to use massive computational power.