File identification

I am looking for a developer who know PE file structure very well and can help me make signtaures keeping in mind that malware bring smaller differenes in the same file so md5 would not work. SO signture has to be such that it can evade such tricks so signtaure can be very strong but not loose as well to not detect different files. Also, I need to find a way to extract/decrypt file on runtime without hurting the original pc so that I can search for the file signature in that. I can provide samples. Do not give me canned bids. Only answer if you understand what I wrote and have expereince working on similar things in the past