The ''bomba'', or ''bomba kryptologiczna'' (Polish for "bomb" or "cryptologic bomb"), was a special-purpose machine designed around October 1938 by Polish Cipher Bureau cryptologist

Marian Rejewski Marian Adam Rejewski (; 16 August 1905 – 13 February 1980) was a Polish mathematician and cryptologist who in late 1932 reconstructed the sight-unseen German military Enigma cipher machine, aided by limited documents obtained by French mil ...

to break German Enigma-machine ciphers.

Etymology

How the machine came to be called a "bomb" has been an object of fascination and speculation. One theory, most likely apocryphal, originated with Polish engineer and army officer Tadeusz Lisicki (who knew Rejewski and his colleague

Henryk Zygalski Henryk Zygalski (; 15 July 1908 – 30 August 1978) was a Polish mathematician and cryptologist who worked at breaking German Enigma ciphers before and during World War II. Life Zygalski was born on 15 July 1908 in Posen, German Empire (now Pozn ...

in wartime Britain but was never associated with the Cipher Bureau). He claimed that

Jerzy Różycki Jerzy Witold Różycki (; Vilshana, Ukraine, 24 July 1909 – 9 January 1942, Mediterranean Sea, near the Balearic Islands) was a Polish mathematician and cryptologist who worked at breaking German Enigma-machine ciphers before and during World ...

(the youngest of the three Enigma cryptologists, and who had died in a Mediterranean passenger-ship sinking in January 1942) named the "bomb" after an ice-cream dessert of that name. This story seems implausible, since Lisicki had not known Różycki. Rejewski himself stated that the device had been dubbed a "bomb" "for lack of a better idea". Perhaps the most credible explanation is given by a Cipher Bureau technician, Czesław Betlewski: workers at B.S.-4, the Cipher Bureau's German section, christened the machine a "

bomb A bomb is an explosive weapon that uses the exothermic reaction of an explosive material to provide an extremely sudden and violent release of energy. Detonations inflict damage principally through ground- and atmosphere-transmitted mechan ...

" (also, alternatively, a "

washing machine A washing machine (laundry machine, clothes washer, washer, or simply wash) is a home appliance used to wash laundry. The term is mostly applied to machines that use water as opposed to dry cleaning (which uses alternative cleaning fluids and ...

" or a "

mangle Mangle can refer to: * Mangle (machine), a mechanical laundry aid consisting of two rollers * Box mangle, an earlier laundry mangle using rollers and a heavy weight * Mangled packet, in computing * Mangrove, woody trees or shrubs * Name mangling ...

") because of the characteristic muffled noise that it produced when operating. A top-secret U.S. Army report dated 15 June 1945 stated: :A machine called the "bombe" is used to expedite the solution. The first

machine A machine is a physical system using power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecul ...

was built by the Poles and was a hand operated multiple enigma machine. When a possible solution was reached a part would fall off the machine onto the floor with a loud noise. Hence the name "bombe". The U.S. Army's above description of the Polish ''bomba'' is both vague and inaccurate, as is clear from the device's description at the end of the second paragraph of the "

History History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...

" section, below: "Each bomb... essentially constituted an ''electrically powered'' aggregate of ''six'' Enigmas..." Determination of a solution involved no disassembly ("a part... fall ngoff") of the device.

Background

The German Enigma used a combination key to control the operation of the machine: rotor order, which rotors to install, which ring setting for each rotor, which initial setting for each rotor, and the settings of the ''stecker'' plugboard. The rotor settings were trigrams (for example, "NJR") to indicate the way the operator was to set the machine. German Enigma operators were issued lists of these keys, one key for each day. For added security, however, each individual message was encrypted using an additional key modification. The operator randomly selected a trigram rotor setting for each

message A message is a discrete unit of communication intended by the source for consumption by some recipient or group of recipients. A message may be delivered by various means, including courier, telegraphy, carrier pigeon and electronic bus. A ...

(for example, "PDN"). This message key would be typed twice ("PDNPDN") and

encrypt In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can deci ...

ed, using the daily key (all the rest of those settings). At this point each operator would reset his machine to the message key, which would then be used for the rest of the message. Because the configuration of the Enigma's rotor set changed with each depression of a key, the repetition would not be obvious in the

ciphertext In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintex ...

since the same

plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted. Overview With the advent of comp ...

letters would encrypt to different ciphertext letters. (For example, "PDNPDN" might become "ZRSJVL.") This procedure, which seemed reasonably secure to the Germans, was nonetheless a

cryptographic Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or '' -logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adv ...

malpractice, since the first insights into Enigma encryption could be inferred from seeing how the same character string was encrypted differently two times in a row.

History

Using the knowledge that the first three letters of a message were the same as the second three, Polish mathematician–

cryptologist This is a list of cryptographers. Cryptography is the practice and study of techniques for secure communication in the presence of third parties called adversaries. Pre twentieth century * Al-Khalil ibn Ahmad al-Farahidi: wrote a (now lost) bo ...

was able to determine the internal wiring of the Enigma machine and thus to reconstruct the logical structure of the device. Only general traits of the machine were suspected, from the example of the commercial Enigma variant, which the Germans were known to have been using for diplomatic communications. The military versions were sufficiently different to present an entirely new problem. Having done that much, it was still necessary to check each of the potential daily keys to break an encrypted message (i.e., a "ciphertext"). With many thousands of such possible keys, and with the growing complexity of the Enigma machine and its keying procedures, this was becoming an increasingly daunting task. In order to mechanize and speed up the process, Rejewski, a civilian mathematician working at the Polish General Staff's Cipher Bureau in

Warsaw Warsaw ( pl, Warszawa, ), officially the Capital City of Warsaw,, abbreviation: ''m.st. Warszawa'' is the capital and largest city of Poland. The metropolis stands on the River Vistula in east-central Poland, and its population is officiall ...

, invented the ''"bomba kryptologiczna"'' (cryptologic bomb), probably in October 1938. Each bomb (six were built in Warsaw for the Cipher Bureau before September 1939) essentially constituted an electrically powered aggregate of six Enigmas and took the place of some one hundred workers. Enigma-plugboard

The bomb method was based, like the Poles' earlier

"grill" method The grill method ( pl, metoda rusztu), in cryptology, was a method used chiefly early on, before the advent of the cyclometer, by the mathematician-cryptologists of the Polish Cipher Bureau (''Biuro Szyfrów'') in decrypting German Enigma machi ...

, on the fact that the plug connections in the commutator ("plugboard") did not change all the letters. But while the grill method required unchanged ''pairs'' of letters, the bomb method required only unchanged letters. Hence it could be applied even though the number of plug connections in this period was between five and eight. In mid-November 1938, the bombs were ready, and the reconstructing of daily keys now took about two hours.

, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys...", Appendix C to Władysław Kozaczuk, ''Enigma'', 1984, p. 242. Up to July 25, 1939, the Poles had been breaking Enigma messages for over six and a half years without telling their

French French (french: français(e), link=no) may refer to: * Something of, from, or related to France ** French language, which originated in France, and its various dialects and accents ** French people, a nation and ethnic group identified with Franc ...

and

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories, and Crown Dependencies. ** Britishness, the British identity and common culture * British English, ...

allies An alliance is a relationship among people, groups, or states that have joined together for mutual benefit or to achieve some common purpose, whether or not explicit agreement has been worked out among them. Members of an alliance are called ...

. On December 15, 1938, two new rotors, IV and V, were introduced (three of the now five rotors being selected for use in the machine at a time). As Rejewski wrote in a 1979 critique of appendix 1, volume 1 (1979), of the official history of ''British Intelligence in the Second World War'', "we quickly found the iringswithin the ew rotors but

heir Inheritance is the practice of receiving private property, titles, debts, entitlements, privileges, rights, and obligations upon the death of an individual. The rules of inheritance differ among societies and have changed over time. Offic ...

introduction ..raised the number of possible sequences of drums from 6 to 60 ..and hence also raised tenfold the work of finding the keys. Thus the change was not qualitative but quantitative. We would have had to markedly increase the personnel to operate the bombs, to produce the

perforated sheets The method of Zygalski sheets was a cryptologic technique used by the Polish Cipher Bureau before and during World War II, and during the war also by British cryptologists at Bletchley Park, to decrypt messages enciphered on German Enigma mac ...

(60 series of 26 sheets each were now needed, whereas up to the meeting on July 25, 1939, we had only two such series ready) and to manipulate the sheets."

, "Remarks on Appendix 1 to ''British Intelligence in the Second World War'' by F.H. Hinsley", p. 80.

Harry Hinsley Sir Francis Harry Hinsley, (26 November 1918 – 16 February 1998) was an English historian and cryptanalyst. He worked at Bletchley Park during the Second World War and wrote widely on the history of international relations and British Int ...

suggested in ''British Intelligence...'' that the Poles decided to share their Enigma-breaking techniques and equipment with the French and British in July 1939 because they had encountered insuperable technical difficulties. Rejewski rejected this: "No, it was not ryptologicdifficulties ..that prompted us to work with the British and French, but only the deteriorating political situation. If we had had no difficulties at all we would still, or even the more so, have shared our achievements with our allies as our contribution to the struggle against Germany."

Notes

References

* Władysław Kozaczuk, ''Enigma: How the German Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two'', edited and translated by

Christopher Kasparek Christopher Kasparek (born 1945) is a Scottish-born writer of Polish descent who has translated works by numerous authors, including Ignacy Krasicki, Bolesław Prus, Florian Znaniecki, Władysław Tatarkiewicz, Marian Rejewski, and Władysław ...

, Frederick, MD, University Publications of America, 1984, {{ISBN, 0-89093-547-5. *

, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods," Appendix C to Władysław Kozaczuk, ''Enigma'', 1984, pp. 241–45. *

, "How the Polish Mathematicians Broke Enigma," Appendix D to Władysław Kozaczuk, ''Enigma'', 1984, pp. 246–71. *

, "The Mathematical Solution of the Enigma Cipher," Appendix E to Władysław Kozaczuk, ''Enigma'', 1984, pp. 272–91. *

, "Remarks on Appendix 1 to ''British Intelligence in the Second World War'' by F.H. Hinsley", translated by

, ''

Cryptologia ''Cryptologia'' is a journal in cryptography published six times per year since January 1977. Its remit is all aspects of cryptography, with a special emphasis on historical aspects of the subject. The founding editors were Brian J. Winkel, Davi ...

: a Quarterly Journal Devoted to All Aspects of

Cryptology Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

'', vol. 6, no. 1 (January 1982), pp. 75–83. *

, "How Polish Mathematicians Deciphered the Enigma", Annals of the History of Computing, Vol. 3, No. 3, Juli 1981, pp. 213-234
The US 6812 Division Bombe Report Eastcote 1944

External links