A programmer has developed a technique to unlock computers infected with
Petya ransomware and has made it available at no cost. The technique
requires extracting information from the computer's hard drive, which
may be beyond the scope of some users' abilities. Another tool, which is
somewhat simpler to use, extracts the required data. It has also been
posted to the Internet.
Internet Storm Center:https://isc.sans.edu/forums/diary/Tool+Released+to+Decrypt+Petya+Ransomware+Infected+Disks/20929/