The Bletchley Park Codebreakers
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basic setting see Grundstellung.
B-Dienst (Beobachtungsdienst – observation service). Cover name for the Kriegsmarine’s codebreaking section.
bigram tables (naval Enigma) sets of tables which substituted pairs of letters (e.g. AA=DF, AB=UA, and so on); used to encode the indicator groups in the Kenngruppenbuch indicating system for naval Enigma.
BJ (blue jacket) decrypt being circulated to a government department (derived from the distinctive blue file cover).
blist Bannister list – a register of Enigma messages, listing important components such as call signs, length of messages etc. (see example in Appendix IV). Designed to help the detection of cillies and the identification of messages with cribs.
bombe ultra-fast machine for recovering Enigma daily keys by testing a crib and its implications, at all possible rotor orders and initial settings.
BP Bletchley Park.
BRUSA British United States Agreement of May 1943 (also known as the Travis-Strong Agreement), between the United States War Department and GC&CS on attacking the military codes and ciphers of the Axis powers.
‘C’ the ‘Chief’ or head of the British Secret Intelligence Service.
cilli a German mistake, found by Dilly Knox, in using the rotor finishing positions in one part of a multi-part Enigma message as the Grund of the next part. Derived from CIL, the Grund of the message in which the mistake was first discovered.
cipher a cryptographic system in which letters or numbers represent plain-text units (generally single letters) in accordance with agreed rules.
cipher indicator group (naval) group indicating the cipher for a message (and therefore the key-lists to look up when enciphering or deciphering it).
cipher text text produced by a cipher.
closure the linking of the same letter in a chain in an Enigma menu (e.g., ACHIA) that returns to its starting point.
code a cryptographic system, generally set out in a codebook, in which groups of letters or numbers represent plain-text units of varying lengths.
Coral the US Navy cover name for a cipher machine (JNA-20) used by Japanese naval attachés. Like Purple (q.v.), it incorporated telephone selector switches, not rotors.
counter Enigma (German Zählwerk) the Abwehr three-rotor Enigma machine using rotors with 11, 15 and 17 notches, but without a plugboard.
crib probable plain-text, which for Enigma was generally derived from a re-enciphered message (whether using Enigma or a manual cipher) or standard message (e.g., ‘nothing to report’).
CSS C hief, Secret Intelligence Service (‘C’).
depth the correct alignment of two or more cipher texts that have been enciphered by the same key.
DF direction finding – locating the position of a transmission by plotting two or more bearing lines.
diagonal board a circuit in the bombes that eliminated a considerable number of superfluous stops. By enabling the effective use of menus that did not consist entirely of closures, it greatly increased the power and flexibility of the bombes.
discriminant (Enigma - German Kenngruppe) a group showing the cipher being used.
doubly encipher to encipher something (e.g. text or a message key) twice (cf. Offizier).
dud a ciphered message which cannot be deciphered because of a faulty message setting or discriminant.
Duenna a US Navy machine which used long cribs to find the wiring of the rewirable Enigma reflector, UKD.
enciphered code code enciphered by a cipher system (generally a series of random figures known as an additive). The ‘additive’ figures are lined up under the encoded message, and added to the code digits using non-carrying arithmetic (5 plus 7 producing 2 rather than 12) to produce the enciphered message.
false stop a position at which a bombe stopped, but giving an impossible result for the Stecker (e.g., B steckered to X, but also to Y).
FECB Far East Combined Bureau. British intelligence organization, covering all fields of intelligence, including special intelligence – interception, breaking and analysis of foreign encoded radio messages. Based in Hong Kong from 1934 and in Singapore from September 1939 until January 1942.
female (Enigma) a letter in the second group of a doubly enciphered Enigma message key, which repeats a letter in the corresponding position in the first group (e.g. AFO CFK).
Fish GC&CS cover name for traffic enciphered on the Sturgeon or Tunny teleprinter cipher machines.
Freebornery the punched card section under Frederic Freeborn.
FRUMEL Fleet Radio Unit (Melbourne). US Navy wartime intercept and codebreaking organization based in Melbourne, Australia.
FRUPAC Fleet Radio Unit (Pacific). US Navy intercept and codebreaking organization in Hawaii.
garble a distorted part of a message.
GC&CS the Government Code and Cypher School.
Green (later renamed Greenshank) an intractable Enigma cipher.
Grund short for Grundstellung (q.v.).
Grundstellung (Enigma) the basic initial position of the rotors at which the message key is enciphered or deciphered.
Hagelin C-38 a mechanical cipher machine invented by Boris Hagelin, and used by the Italian navy; very similar to the Hagelin M 209 adopted by the US Army.
Heer the German Army in the Second World War
Herivel tip a method used to deduce the daily Ringstellungen, especially in Luftwaffe Enigma ciphers, from a series of Grundstellungen at the start of a cipher period. Named after John Herivel, who first realized that some operators would use the ring settings as Grundstellungen in this way.
Herivelismus the application of the Herivel tip.
Hut 3 the GC&CS section responsible for translating and analysing Enigma decrypts received from Hut 6, together with related intelligence, and for distributing the resulting intelligence.
Hut 4 the CC&CS section responsible for translating, analysing Enigma decrypts received from Hut 8, and for all naval cryptanalysis, except Enigma, and for sending the translated Enigma and other naval decrypts to the Admiralty.
Hut 6 the GC&CS section responsible for solving Heer, Luftwaffe and Railway Enigma ciphers.
Hut 8 the GC&CS section responsible for solving Kriegsmarine Enigma ciphers.
indicator a group of letters or symbols showing the cipher system being used.
indicator groups (naval Enigma) two groups setting out the cipher recognition group and procedure indicator group (from which the message key was derived).
ISK Illicit Services, Knox (also Intelligence Services, Knox).
ISOS Illicit Services, Oliver Strachey (also Intelligence Services, Oliver Strachey).
Jeffreys sheets a catalogue of the effect of any two rotors and the reflector in Enigma. Not to be confused with Zygalski sheets (q.v.).
JIC Joint Intelligence Committee.
JN Japanese naval. Used with a number to denote a Japanese naval code or cipher, such as JN-25 (the principal naval code).
JNA Japanese naval attaché.
JNA-20 See Coral
JN-25 the principal Japanese Navy general operational code, a superenciphered code introduced in June 1939 and used in numerous versions throughout the war. The JN-25 code and cipher additive books were allocated different letters and numbers by the Allies, as in JN-25B7, where ‘B’ denoted the ‘Baker’ codebook being used, and the final figure (‘7’ here), the relevant additive book.
kana Japanese syllable depicting a phonetic sound.
kanji the familiar Japanese ideographs on which the written language is based.
Kenngruppenbuch (naval Enigma) recognition group book; a book containing trigrams, used with the main naval Enigma indicating system (see Appendix III).
key a) as respects Enigma, an Enigma cipher, such as Red, Phoenix, etc.; b) as respects Enigma, the machine set-up for a day or period, consisting of the Walzenlage, Ringstellungen and Stecker (also the Grundstellung for Kriegsmarine Enigma ciphers); c) generally, a series of numbers or symbols used to encipher text.
key-list a list of keys, generally daily, for a cipher.
KGB Komitet Gosudarstvennoi Bezopasnosti, or Committee for State Security, the commonly understood title for the Russian state secret services. These had a variety of different titles throughout the period covered. The title KGB was not introduced until March 1954 and was abolished in October 1991, but for ease of understanding it is used throughout.
Kriegsmarine the German Navy in the Second World War.
Luftwaffe the German Air Force in the Second World War.
MI1b the department of British military intelligence dealing with Sigint during the First World War.
MI5 the Security Service, title dates from the First World War and the immediate aftermath of the Armistice when it was part of Army intelligence and in theory its only role was to root out subversion within the armed forces.
MI6 common wartime name for the British Secret Intelligence Service, technically the Army intelligence branch that liaised with SIS. It was not introduced until 1940, but for ease of understanding it is used throughout.
MI8 the department of British military intelligence dealing with Sigint during the Second World War.
MND Marinenachrichtendienst (Kriegsmarine Communications Service).
M3 the Kriegsmarine three-rotor Enigma machine.
M4 the Kriegsmarine four-rotor Enigma machine.
menu a series of linked plain-text/cipher text letters used for giving instructions to bombe operators on setting up the bombes.
message key (Enigma) the rotor starting positions for a specific Enigma signal.
message setting the message key (q.v.).
NID25 Naval Intelligence Department 25. The Royal Navy’s Sigint branch during the First World War, better known as Room 40 from the room in the Old Admiralty Buildings in Whitehall that it occupied.
NSA National Security Agency.
Offizier a system for doubly enciphering naval Enigma signals, which ensured that only officers could read their substantive text.
OKH Oberkommando des Heeres (High Command of the German Army).
OKW Oberkommando der Wehrmacht (High Command of the Wehrmacht).
OKW/Chi OKW’s Amtsgruppe Wehrmachtnachrichtenverbindungswesen Chiffrierabteilung the section responsible for cipher security.
OTP one-time pad. A series of random additives intended for use once only. If used correctly, the system is unbreakable.
perforated sheets see Zygalski sheets.
psilli psychological cilli. An Enigma message setting which is so closely related to the message Grundstellung that it can be guessed (e.g., Grund ‘HIT’ might give message setting ‘LER’). Also a guessable keyboard sequence, such as ‘QWE’.
Purple the Japanese diplomatic cipher machine, angoo-ki taipu b (Type B machine), codenamed Purple by the US Army.
RAF Royal Air Force.
Red the principal Luftwaffe Enigma cipher (codename assigned by Hut 6).
Red (Japanese) the Japanese diplomatic cipher machine, angoo-ki taipu a (Type A machine), codenamed Red by the Americans.
re-encipherment the encipherment of the same plain-text in two or more ciphers.
Ringstellung ring setting. The setting of the ring (or tyre) on an Enigma rotor.
romaji system of transliteration allowing kana to be spelt out in Roman letters.
rotor (Enigma) rotating disc (or wheel) with randomly wired electric contacts used for encipherment in Enigma.
rotor order (Enigma) the order in which rotors were inserted in Enigma (e.g., III, I, IV), looking at the machine from the front.
R/T radio telephone.
Schlüsselkenngruppe (naval Enigma) see cipher indicator group.
Schlüsselzusatz cipher attachment.
SD the Sicherheitsdienst (the intelligence service of the Nazi party).
Sigint signals intelligence. All intelligence derived from studying radio and other signals.
SIS (American) Signal Intelligence Service – the US Army’s codebreaking unit (the name was changed on several occasions during the war).
SIS (British) the Secret Intelligence Service (MI6).
SKL Seekriegsleitung (the German naval war staff).
SOE Special Operations Executive
Spruchschlüssel see message key.
SS Schutzstaffeln. Protection squads formed in the 1920s, which became a powerful organization in the Nazi party, and Germany, with a military section, the Waffen SS.
SSA Signal Security Agency. The codebreaking unit of the US Army (which had a variety of names during the war; cf. SIS (American)).
SSD Signal Security Detachment. A codebreaking section in the US Army.
Stecker short for Steckerverbindungen (plug connections).
Steckerverbindungen the plug connections in Enigma’s plugboard.
Stichwort (naval Enigma) cue word – a procedure modifying a daily key when a key-list had been compromised.
Stop the position at which a bombe stopped, corresponding to a possible Enigma key.
Sturgeon GC&CS codename for the Siemens and Halske T52 series of teleprinter cipher machines.
success rate decrypts as a percentage of the signals intercepted.
superenciphered code see enciphered code.
SZ 40 or 42 the Lorenz Schlüsselzusatz (cipher attachment) for teleprinters.
TA see traffic analysis.
TJAO Temporary Junior Administrative Officer
traffic radio signals, generally encrypted, between two or more stations, or using a common code or cipher.
traffic analysis the study of the external characteristics of signals (such as call signs and frequencies used) in order to derive intelligence.
trigram a group of three figures or letters.
Tunny GC&CS codename for the Lorenz SZ 40/42 teleprinter cipher attachment.
Typex the British cipher machine, based on Enigma (but without an entry plugboard). Never broken by the German codebreakers.
Uhr a device which made Enigma’s plugboard largely nonreciprocal (see Chapter 19).
UKD see Umkehrwalze D.
Ultra ‘special intelligence’ – intelligence derived from high-grade codes and ciphers, such as Enigma and Fish.
Umkehrwalze (Enigma) reflector.
Umkehrwalze D (Enigma) reflector Dora (UKD), which was rewirable in the field as part of an Enigma key (see Chapter 19). Used almost exclusively by the Luftwaffe.
Walzenlage (Enigma) rotor order (e.g., II, V, III).
WEC Wireless Experimental Centre. British signals intelligence site set up just outside Delhi in June 1942.
WED Wireless Experimental Depot. British intercept and decryption site based at Abbottabad on the North West Frontier, set up in the 1920s.
Wehrmacht all three branches of the German armed forces in the Second World War.
Werftschlüssel dockyard cipher – a manual cipher system used by the Kriegsmarine.
wheel see rotor.
Wren member of the WRNS (q.v.).
WRNS Women’s Royal Naval Service.
Y service the intercept and DF service (before October 1943, the service also dealt with traffic analysis and broke some lowgrade codes and ciphers).
Zählwerk Enigma see counter Enigma.
Zygalski sheets lettered sheets with holes punched in them, showing which combinations of rotor starting positions and wheel orders produced females. By suitably aligning the relevant sheets on top of each other, the Ringstellungen and rotor order were revealed by the coincidence of holes in some sheets.
NOTES ON CONTRIBUTORS
Richard J. Aldrich is a Professor of International Security at the University of Warwick where he leads the AHRC-funded research project ‘Landscapes of Secrecy’ on the history of the CIA. His previous publications include Intelligence and the War Against Japan: Britain, America and the Politics of Secret Service, The Hidden Hand: Britain, America and Cold War Secret Intelligence and the widely acclaimed GCHQ: The Uncensored Story of Britain’s Most Secret Intelligence Ag
ency.
David Alvarez is the author of Secret Messages: Codebreaking and American Diplomacy, 1930-1945 and the editor of Allied and Axis Signals Intelligence in World War II. He is a professor at St Mary’s College of California and has served as scholar in residence at the US National Security Agency