Editing Cryptanalysis (section)

====Indicator====
With reciprocal machine ciphers such as the [[Lorenz cipher]] and the [[Enigma machine]] used by [[Nazi Germany]] during [[World War II]], each message had its own key. Usually, the transmitting operator informed the receiving operator of this message key by transmitting some plaintext and/or ciphertext before the enciphered message. This is termed the ''indicator'', as it indicates to the receiving operator how to set his machine to decipher the message.<ref>{{Harvnb|Churchhouse|2002|pp=33, 34}}</ref>

Poorly designed and implemented indicator systems allowed first [[Biuro Szyfrów|Polish cryptographers]]<ref>{{Harvnb|Budiansky|2000|pp=97–99}}</ref> and then the British cryptographers at [[Bletchley Park]]<ref>{{Harvnb|Calvocoressi|2001|p=66}}</ref> to break the Enigma cipher system. Similar poor indicator systems allowed the British to identify ''depths'' that led to the diagnosis of the [[Lorenz cipher|Lorenz SZ40/42]] cipher system, and the comprehensive breaking of its messages without the cryptanalysts seeing the cipher machine.<ref name="Tutte 1998">{{Harvnb|Tutte|1998}}</ref>