It seems you have a lot of people professing they can solve your problem but the fact of the matter is that most ransomware viruses generate special keys per infected user usually something like (public key + master key) = decrypt files. most of the time the time these ransomware programs are impossible to decrypt unless there keys have been confiscated by authorities. I was surprised that google showed virtually nothing for igza4c as this seems to be there file extension. do you recall anything else around the time of infection such as a screen locker any relevant pictures or even a brand such as (coinvault) ?