Glossary

Abwehr The German armed forces intelligence service.

Additive Figures added to a cipher message using non-carrying arithmetic during the super-encipherment process.

Alphabet Paired reciprocal letters in same position on the Enigma machine.

ARCOS All-Russian Co-operative Society, trade organisation which provided cover for Soviet intelligence activities in the UK in the 1920s.

B1A MI5 section that controlled the double agents ostensibly operating in the UK.

Beetle Term invented by Dilly Knox to define two clicks on the same rod, also known as a direct click.

Blue The various Enigma ciphers were originally identified by colours. Blue was the Luftwaffe practice Enigma cipher machine.

Boil A technique invented by Dilly Knox which exploited the fact that no letter could be enciphered as itself. Cipher texts were catalogued on a chart to identify letters that never appeared at certain points in the message and were therefore likely plain text.

Bomba (pl. bomby) Polish electro-mechanical device designed to assist in breaking Enigma keys.

Bombe Ultra-fast electro-mechanical machine for recovering Enigma daily keys by testing a crib and its implications at all possible wheel or rotor orders and initial settings, inspired by but not based on the Polish bomby.

Boxing The process of cataloguing box-shapes, i.e. forming chains of letters from indicators doubly enciphered on a Grundstellung, so that the enciphered indicators

TQZ PYC

POW RTI

will box as TPR.

Box-shapes The patterns formed by enciphered indicators during the pre-war period when the Grundstellung did not change.

BP Bletchley Park.

Buttoning-up A method for recovering the wiring of the rotors used in an Enigma cipher machine that did not have the Stecker or plugboard (See Appendix 3).

‘C’ Title of the head of SIS, known as Chief. ‘C’ was originally derived from the first letter of the surname of the first chief of SIS, Mansfield Cumming. For security reasons, Cumming was only referred to as ‘C’. The title was inherited by his successor, Admiral Hugh Sinclair, by which time it had become an abbreviation for ‘Chief’. It remains in use to this day.

Call-sign The designation given to a wireless station on a communications circuit or network to allow ease of identification, often used in a preamble to identify the originator and intended recipients of the message.

Cilli A German procedural error, first spotted by Dilly Knox, in which the operator uses the rotor finishing positions in one part of a multi-part Enigma message as the Grundstellung for the next part. Derived from CIL, the basic position 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 pre-arranged rules.

Click Confirmations of probable cribs of individual letters. There are two kinds of clicks: direct clicks are those in which both letters of the crib occur side by side on the same rod; Dilly called this a beetle. The other is a cross-click where one of the crib letters is on one rod and the second on the other; Dilly called this a starfish.

Click chart A chart compiled at Dilly’s instigation to show all occurrences of clicks.

Code A cryptographic system, generally set out in a codebook, in which groups of letters or numbers represent plain-text words or phrases.

Comintern Communist International, organisation set up by Moscow with the intention of spreading communism worldwide.

Crab Term invented by Dilly Knox to define two lobsters four places apart on the key-block.

Crib Probable plain text guessed at from previous usage and tested out against the cipher text to break a message.

Cyclometer A machine devised by Polish codebreaker Marian Rejewski comprising two sets of rotors connected by electric wires which he used to produce a catalogue of early Enigma rotor cycles.

Depth The correct alignment of ciphered text that has been enciphered by the same length of key.

Diagonal The order in which keys on the Enigma machine were wired to the entry plate, QWERTZU in the un-Steckered machines, ABCDE in the Wehrmacht machines.

DID Director Intelligence Division. British head of naval intelligence in the First World War.

Direction-finding Locating the sender of a message by plotting bearings to the origin of the radio signals received at two or more locations.

Discriminant (German Kenngruppe) A group in the preamble showing the cipher system in use.

DNI Director Naval Intelligence. British head of naval intelligence in the Second World War.

Female 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.

FUSAG Notional First US Army Group alleged to be under General Patton that was central to the Allied D-Day deception plans suggesting the main attack would be on the Pas de Calais.

GC&CS Government Code and Cypher School, the British codebreaking and cipher security organisation between 1919 and 1945.

GGG Abwehr Enigma used between Berlin and stations in Spain.

Grundstellung The basic original position of the rotors at which the message key is enciphered or deciphered.

Herivel tip A method used to deduce the daily Ringstellungen from a series of Grundstellungen at the start of the cipher period. Named after John Herivel, who first realised that some operators would use the ring settings as Grundstellungen in this way.

Hollerith Punched-card equipment used for rapid searches of data at Bletchley Park.

Hut 3 The section at Bletchley Park which issued intelligence reports based on the German army and Luftwaffe Enigma messages deciphered in Hut 6.

Hut 4 The naval section at Bletchley Park, led by Frank Birch, which issued intelligence reports based on the German naval Enigma messages deciphered in Hut 8.

Hut 6 The section at Bletchley Park which deciphered German army and Luftwaffe Enigma messages.

Hut 8 The section at Bletchley Park which deciphered German naval Enigma messages.

Indicators A group of letters or symbols showing the cipher system being used.

ISK Illicit Services Knox, also Intelligence Services Knox, the designation given to both the section that deciphered German intelligence service Enigma machines and the resulting decodes throughout the war.

ISOS Illicit Services Oliver Strachey, also Intelligence Services Oliver Strachey, the designation given to both the section that deciphered German intelligence service hand ciphers and the resulting decodes throughout the war.

Jeffreys sheets A catalogue of the effect of any two wheels or rotors and the reflector in the Enigma machine. Not to be confused with Zygalski sheets.

K model Improved early commercial Enigma machine with turnover on the wheel instead of the tyre.

Key A series of numbers or symbols used to encipher text. In terms of Enigma, this meant the initial settings of the various parts of the machine for a given period of time, usually a day.

Key-block A group of indicators enciphered using the same Grundstellung.

Kriegsmarine The name used by the German navy from 1935 to 1945.

Lobster Term invented by Dilly Knox to define a message enciphered using an Abwehr Enigma machine, in which all four wheels turn over at the same time. Also known as a four-wheel turnover.

Luftwaffe German air force.

Mask Codename of the 1930s operation, in which Dilly Knox played a leading role, to intercept and decipher messages between Moscow and Comintern representatives worldwide.

Menu A series of linked plain and cipher pairs based on cribs or predictions of original plain text used as instructions for setting up a bombe.

MEW Ministry of Economic Warfare.

MI1b The First World War military intelligence department that dealt with signals intelligence, both collection and decryption.

MI5 British domestic counter-espionage and security service, more properly known as the Security Service.

Netz See Zygalski sheets.

NID Naval Intelligence Division, the Admiralty’s intelligence organisation.

NID25 Naval Intelligence Division 25, the Royal Navy’s signals intelligence branch during the First World War, better known as Room 40. This is where Dilly Knox worked and was the inspiration for Alice in NID25.

OIC Operational Intelligence Centre, the Second World War naval intelligence organisation which used co-ordinated intelligence to plot enemy shipping worldwide.

Pinch A piece of cryptographic material, which could be anything from a list of keys to a cipher machine, stolen or captured from the enemy and used to assist in codebreaking.

Preamble The information given at the start of a message, normally in a standard format, which gives such details as the message serial number; the originator; the intended recipients; the time and date the message was initiated; the priority; security classification; and the discriminants and keys in use.

Psilli A psychological cilli. An Enigma message setting which so closely related to the message Grundstellung that it could be guessed at, e.g. a Grundstellung of HIT might be followed by a message setting of LER.

QWERTZU The name given by Dilly Knox to the ‘diagonal’, the order in which the keys on the Enigma machine were wired to the entry plate. It derives from the order of the top line of the keys on a German typewriter, which was the layout used for the Enigma keys.

Radio Security Service Intercept and analysis organisation originally part of MI5, later part of SIS Section V, which dealt with illicit radio stations operating in the UK.

Red The colour coding given to the main Luftwaffe Enigma cipher.

Reichsmarine Original post-First World War name for the German navy, which was changed to Kriegsmarine in 1935.

Reichswehr The original name for the German armed forces following the First World War, changed to Wehrmacht in 1935.

Ringstellung Ring setting. The setting of the ring or tyre on an Enigma rotor or wheel.

Rodding Technique devised by Dilly Knox in 1937 to break an Enigma cipher machine that did not have the Stecker or plugboard (See Appendix 2).

Rotor Rotating disc on an Enigma cipher machine with wired electrical contacts which, with a number of other rotors, contributes to the encipherment process. Also known as a wheel, from the original German Walze.

Saga Method of ‘boxing’ throw-on indicators.

SD Sicherheitsdienst, the Nazi Party’s internal intelligence service, effectively Nazi Germany’s civilian intelligence service during the Second World War. It also took over all functions of the Abwehr in 1944.

Section V The SIS counter-espionage section during the Second World War.

Section VIII The SIS communications section during the Second World War.

Sigint Signals intelligence – the general term for the processes of interception of electronic signals, codebreaking, analysis and intelligence processing.

SIS Secret Intelligence Service, British foreign intelligence service, more commonly known as MI6.

Slides An insecure method of producing the indicators in which the operator slides his fingers over several adjacent keys in order to produce the indicator, e.g. WER.

SLU Special Liaison Unit, an intelligence unit attached to Allied commanders which passed them ULTRA intelligence.

Starfish Term invented by Dilly Knox to define two clicks in which one is on one rod and the second is on another rod, also known as a cross-click.

Stecker Shortened form of Steckerverbindung, the connections used on the plugboard added to the German armed forces Enigma machines to provide greater security.

Substitution cipher A cipher in which one letter is substituted by another but retains its position in the message.

Super-encipherment A system in which an already encrypted message is enciphered to give it an increased level of security.

Supermarina The Italian Admiralty.

Throw-on indicators A pair of letters representing two encipherments of the same letter at two different positions in indicators that have been enciphered twice on a Grundstellung.

Traffic The messages passing on a communications network or circuit.

Traffic analysis The study of wireless communication networks and the exploitation of operators’ signals procedure and plain language conversations.

Transposition cipher A cipher in which the positions of individual letters or figures change their positions within a message.

Turnover Movement of a wheel produced by the movement of the next wheel to its right.

Typex The British cipher machine, based on Enigma but crucially never broken by the Germans.

Tyres Alternative name for the rings on the rotors or wheels.

ULTRA The top secret codeword attached to the security classification applied to intelligence derived from the breaking of high-grade ciphers. The security classification at the top and bottom of such intelligence was rendered as Top Secret Ultra.

Umkehrwalze The reflector which sent the electrical signal back through the wheels or rotors to complete the letter’s encryption.

Wehrmacht All three branches of the German armed forces.

Wheel Rotating disc on an Enigma cipher machine with wired electrical contacts which, with a number of other wheels, contributes to the encipherment process. Use of the word ‘wheel’ derives from the original German Walze. Also known as a rotor.

Wheel track Sequence of turnovers on the Abwehr machine wheels.

Y Service The intercept and direction-finding service, which until October 1943 also carried out traffic analysis and broke low-grade codes and ciphers.

Zygalski sheets Lettered sheets with holes punched in them showing which combination of wheel or rotor starting positions and orders produced females. By suitably aligning the relevant sheets on top of each other, the Ringstellungen and the wheel or rotor order were revealed by the coincidence of holes in some sheets. Also known as Netz.