477:, National Security Agency (NSA), Volumes I, 1973, partially released 2008, additional portions declassified October 14, 2015, Quote: The KL-7 "was our first machine designed to serve very large nets which could stand matched plain and cipher text. For the first time, the man in the cryptocenter could take a message and simply type it into the machine as written, without changing the spacing between words, or cutting the message in half and sending the last part first. and without having to paraphrase the message text before it was released."
131:, but if they had a clue about some word or phrase that might be expected to be in the ciphertext, they would have a "wedge," a test to break into it. If their otherwise random attacks on the cipher managed to sometimes produce those words or (preferably) phrases, they would know they might be on the right track. When those words or phrases appeared, they would feed the settings they had used to reveal them back into the whole encrypted message to good effect.
226:, for their most sensitive traffic. These devices were immune to known-plaintext attack; however, they were point-to-point links and required massive supplies of one-time tapes. Networked cipher machines were considered vulnerable to cribs, and various techniques were used to disguise the beginning and ends of a message, including
142:
team would guess some of the plaintext based upon when the message was sent, and by recognizing routine operational messages. For instance, a daily weather report was transmitted by the
Germans at the same time every day. Due to the regimented style of military reports, it would contain the word
147:(German for "weather") at the same location in every message. (Knowing the local weather conditions helped Bletchley Park guess other parts of the plaintext as well.) Other operators, too, would send standard salutations or introductions. An officer stationed in the
82:
A plain language (or code) passage of any length, usually obtained by solving one or more cipher or code messages, and occurring or believed likely to occur in a different cipher or code message, which it may provide a means of
138:, the German High Command was very meticulous about the overall security of the Enigma system and understood the possible problem of cribs. The day-to-day operators, on the other hand, were less careful. The
185:
agents sent a message (written by the
British) to their respective handlers, they frequently obligingly re-encrypted the message word for word on Enigma for onward transmission to Berlin.
162:, strenuous efforts were made to use (and even force the Germans to produce) messages with known plaintext. For example, when cribs were lacking, Bletchley Park would sometimes ask the
208:" was encoded at all positions in the plaintext. The catalogue included every possible position of the various rotors, starting positions, and keysettings of the Enigma.
215:
had likewise exploited "cribs" in the "ANX method" before World War II (the
Germans' use of "AN", German for "to", followed by "X" as a spacer to form the text "ANX").
610:
178:, by obvious reference). The Enigma messages that were soon sent out would most likely contain the name of the area or the harbour threatened by the mines.
514:, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods," Appendix C to
457:, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods," Appendix C to
230:
and adding nonsense padding at both ends. The latter practice resulted in an infamous incident during World War II when the nonsense padding "
603:
188:
When a captured German revealed under interrogation that Enigma operators had been instructed to encode numbers by spelling them out,
596:
112:
term referring to cheating (e.g., "I cribbed my answer from your test paper"). A "crib" originally was a literal or interlinear
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245:, introduced in the mid-1950s, was the first U.S. cipher machine that was considered safe against known-plaintext attack.
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can be solved using a single letter of corresponding plaintext and ciphertext to decrypt entirely. A general
234:" was not nonsensical enough and was misinterpreted as part of the actual message, leading American admiral
474:
273:
89:
494:
Enigma: How the German
Machine Cipher Was Broken, and How It Was Read by the Allies in World War Two
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The
Germans themselves could be very accommodating in this regard. Whenever any of the turned German
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needs several character pairs and some guessing if there are fewer than 26 distinct pairs.
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The idea behind a crib is that cryptologists were looking at incomprehensible
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text—that students might be assigned to translate from the original language.
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The
Bletchley Park 1944 Cryptographic Dictionary formatted by Tony Sale, 2001
43:
619:
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27:
Attack model for cryptanalysis with access to both plaintext and ciphertext
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World War II: Crucible of the
Contemporary World: Commentary and Readings
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55:
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Smith, Michael (2006), "How It Began: Bletchley Park Goes to War", in
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A History of U.S. Communications
Security; the David G. Boak Lectures
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67:
47:
283:
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are typically vulnerable to known-plaintext attack. For example, a
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occurring at the end of a message, is another well-known example.
553:
Colossus: The
Secrets of Bletchley Park's Codebreaking Computers
333:
Colossus: The
Secrets of Bletchley Park's Codebreaking Computers
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Michael Smith, "How It Began: Bletchley Park Goes to War," in
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reviewed decrypted messages and determined that the number "
500:, Frederick, MD, University Publications of America, 1984,
242:
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cutting messages in half and sending the second part first
196:" ("one") was the most common string in the plaintext (
432:
Alan Turing : life and legacy of a great thinker
151:
consistently reported that he had nothing to report.
571:"Nazi Code-Making Enigma Machine Is Up for Auction"
372:"Nazi Code-Making Enigma Machine Is Up for Auction"
618:
429:
701:
200:). He automated the crib process, creating the
78:decryption operation, where it was defined as:
604:
531:The Hut Six Story: Breaking the Enigma Codes
316:The Hut Six Story: Breaking the Enigma Codes
468:
430:Hofstadter, D.; Teuscher, Christof (2004).
611:
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434:. Berlin New York: Springer. p. 455.
46:where the attacker has access to both the
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349:. New York: M. E. Sharpe. p. 240.
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116:of a foreign-language text—usually a
174:(a process that came to be known as
108:The usage "crib" was adapted from a
555:, Oxford: Oxford University Press,
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218:The United States and Britain used
166:to "seed" a particular area in the
24:
257:monoalphabetic substitution cipher
25:
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70:. The term "crib" originated at
62:). These can be used to reveal
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13:
1:
569:Geggel, Laura (29 May 2019).
533:, Harmondsworth: Allen Lane,
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370:Geggel, Laura (29 May 2019).
7:
496:, edited and translated by
405:. New York: Arrow. p.
274:Cryptanalysis of the Enigma
262:
10:
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103:
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522:, 1984, pp. 241–45.
299:
204:, which assumed that "
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32:known-plaintext attack
710:Cryptographic attacks
345:Lee, Loyd E. (1991).
238:to change his plans.
222:systems, such as the
158:At Bletchley Park in
80:
498:Christopher Kasparek
294:Ultra (cryptography)
289:Polish Cipher Bureau
279:Kiss (cryptanalysis)
465:, 1984, pp. 243–44.
516:Władysław Kozaczuk
490:Władysław Kozaczuk
459:Władysław Kozaczuk
236:William Halsey Jr.
149:Qattara Depression
697:
696:
652:Chosen-ciphertext
562:978-0-19-284055-4
549:Copeland, B. Jack
249:Classical ciphers
232:the world wonders
16:(Redirected from
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678:Open key models
640:Chosen-plaintext
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202:Eins Catalogue
153:"Heil Hitler,"
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402:The Code Book
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578:. Retrieved
575:Live Science
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76:World War II
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29:
682:Related-key
211:The Polish
190:Alan Turing
114:translation
64:secret keys
704:Categories
484:References
441:3540200207
129:ciphertext
68:code books
60:ciphertext
54:) and its
50:(called a
687:Known-key
662:Lunchtime
580:31 August
381:31 August
176:gardening
168:North Sea
58:version (
56:encrypted
48:plaintext
657:Adaptive
645:Adaptive
529:(1982),
399:(1999).
318:, p. 78.
284:PC Bruno
263:See also
86:—
83:solving.
38:) is an
551:(ed.),
331:, ed.,
104:History
559:
537:
520:Enigma
504:
463:Enigma
438:
413:
353:
145:Wetter
136:Enigma
300:Notes
269:Cadix
224:5-UCO
172:mines
170:with
122:Greek
118:Latin
110:slang
95:(PDF)
582:2020
557:ISBN
535:ISBN
502:ISBN
436:ISBN
411:ISBN
383:2020
351:ISBN
243:KL-7
241:The
206:eins
194:eins
66:and
52:crib
42:for
30:The
622:in
407:184
120:or
36:KPA
706::
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518:,
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314:,
612:e
605:t
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34:(
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