Seems I have a decoder for #Petya, but it works only if the system was not rebooted after the infection. Petya Ransomware eats your hard drives.
Ransomware is evolving — fast. The new versions of ransomware use strong asymmetrical encryption with long keys so that files cannot be decrypted without the key. The bad guys have started using TOR and payments in bitcoins for the sake of staying totally anonymous. And now there is Petya ransomware which in a certain sense encrypts the whole hard drive all at once instead of encrypting files one by one.