Enigma machine
noun1
Historical A small portable electro-mechanical rotor machine used to encrypt and decrypt secret messages, made famous by Germany in WWII.
2
Figuratively Something which decrypts or makes understandable something enigmatic.
- No one needed an Enigma machine to figure out why Jimmy Carter was recalling his days aboard a nuclear submarine.2004, New Yorker, 9 - 16 August 2004, page 37