Rotor machine
A rotor machine is an electromechanical cipher device whose rotating wired wheels change the substitution after each input.
Definition
A rotor machine routes a signal through wired wheels that implement letter permutations. One or more rotors step as characters are entered, changing the electrical path and producing a polyalphabetic substitution.
Settings and operation
The key can include rotor choice and order, ring settings, starting positions, and—on some machines—a plugboard. Enigma also used a reflector, which made encryption and decryption reciprocal but prevented a letter from encrypting to itself.
Security and cryptanalysis
Rotor machines offered far more changing substitutions than hand ciphers, but procedures, operator mistakes, repeated message keys, and structural properties enabled attacks. They are historically important but provide no modern security.
No. Enigma is one family; other designs used different rotor stepping, wiring, and components.
Stepping changes the substitution from one character position to the next, reducing simple frequency patterns.