During World War II, spying on the Nazis was made difficult by the way their messages to each other were scrambled, or encrypted, using a machine called Enigma.
It was made of a keyboard attached to turning drums and electrical circuits. When a letter was typed, a light came on behind a different letter to use instead in the code, or the ciphertext. Because the machine’s drums rotated, letters lit up different ones each time.
Every day, the Enigma machines would be set up with a new password for the day – the starting positions of the drums. You could only read the original message if you had an Enigma machine and set it with the password used to encrypt that message. By typing in the ciphertext it would light up the original message a letter at a time.
It was fiendishly clever and the Nazis thought it was impossible to crack. They thought all their secret wartime orders were safe.
Message that matters: clever codes can keep secrets secret