Files with enigma file extension can be found as encrypted and renamed files affected by a variant of Coverton ransomware.
ENIGMA file extension - Coverton ransomware affected data
What is enigma file? How to open enigma files?
File type specification:
The enigma file extension is most recently related to a new ransomware labeled as Coverton.
Much like similar ransomware it encrypts users files and demands ransom to be paid in bitcoins.
WARNING!: It seems that the authors of this particular ransomware are either amateurs or really evil, because even when you pay the ransom you won't get your data back and they remain encrypted.