# Reflector (cipher machine)

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{{Unreferenced|date=April 2026}}
A '''reflector''', in [cryptology](/source/cryptology), is a component of some [rotor cipher machines](/source/rotor_machine), such as the [Enigma machine](/source/Enigma_machine), that sends electrical impulses that have reached it from the machine's [rotors](/source/rotor_machine), back in reverse order through those rotors. The reflector simplified using the same machine setup for encryption and decryption, but it creates a weakness in the encryption: with a reflector the encrypted version of a given letter can never be that letter itself. That limitation aided World War II code breakers in [cracking Enigma encryption](/source/Cryptanalysis_of_the_Enigma). The comparable WWII U.S. cipher machine, [SIGABA](/source/SIGABA), did not include a reflector. 

thumb|250px|The scrambling action of the Enigma rotors shown for two consecutive letters — current is passed into set of rotors, around the reflector, and back out through the rotors again.

Note: The greyed-out lines represent other possible circuits within each rotor, which are hard-wired to contacts on each rotor.

Letter {{mono|A}} encrypts differently with consecutive key presses, first to {{mono|G}}, and then to {{mono|C}}. This is because the right hand rotor has stepped, sending the signal on a completely different route.

== Other names ==
The reflector is also known as the '''reversing drum''' or, from the German, the '''''Umkehrwalze''''' or '''''UKW'''''.

{{crypto-stub}}

Category:Rotor machines

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Adapted from the Wikipedia article [Reflector (cipher machine)](https://en.wikipedia.org/wiki/Reflector_(cipher_machine)) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Reflector_(cipher_machine)?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.