The rotor-cipher machine Another early instance of a side-channel attack occurred in 1965 when the British MI5 agency attempted to crack a cipher used by the Egyptian Embassy in London.

After every key type, the rotors would increment forward, ensuring that the encryption of the next letter would be different.

A rare 1944 four-rotor M4 Enigma cipher machine, considered one of the hardest challenges for the Allies to decrypt, has sold at a Christie's auction for £347,250 ($437,955).