466:, 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."
120:, 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.
215:, 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
131:
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
136:(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
71:
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
127:, 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
174:
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.
599:
151:, 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
197:" 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.
204:
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").
592:
167:, 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.
503:, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods," Appendix C to
446:, "Summary of Our Methods for Reconstructing ENIGMA and Reconstructing Daily Keys, and of German Efforts to Frustrate Those Methods," Appendix C to
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and adding nonsense padding at both ends. The latter practice resulted in an infamous incident during World War II when the nonsense padding "
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When a captured German revealed under interrogation that Enigma operators had been instructed to encode numbers by spelling them out,
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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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234:, 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
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223:" was not nonsensical enough and was misinterpreted as part of the actual message, leading American admiral
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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
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36:
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Attack model for cryptanalysis with access to both plaintext and ciphertext
336:
World War II: Crucible of the
Contemporary World: Commentary and Readings
272:
536:
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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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.
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Colossus: The
Secrets of Bletchley Park's Codebreaking Computers
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Colossus: The
Secrets of Bletchley Park's Codebreaking Computers
231:
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316:
Michael Smith, "How It Began: Bletchley Park Goes to War," in
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reviewed decrypted messages and determined that the number "
489:, Frederick, MD, University Publications of America, 1984,
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cutting messages in half and sending the second part first
185:" ("one") was the most common string in the plaintext (
421:
Alan Turing : life and legacy of a great thinker
140:
consistently reported that he had nothing to report.
560:"Nazi Code-Making Enigma Machine Is Up for Auction"
361:"Nazi Code-Making Enigma Machine Is Up for Auction"
189:). He automated the crib process, creating the
69:
67:decryption operation, where it was defined as:
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8:
520:The Hut Six Story: Breaking the Enigma Codes
305:The Hut Six Story: Breaking the Enigma Codes
419:Hofstadter, D.; Teuscher, Christof (2004).
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423:. Berlin New York: Springer. p. 455.
35:where the attacker has access to both the
338:. New York: M. E. Sharpe. p. 240.
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105:of a foreign-language text—usually a
7:
163:(a process that came to be known as
97:The usage "crib" was adapted from a
544:, Oxford: Oxford University Press,
207:The United States and Britain used
155:to "seed" a particular area in the
246:monoalphabetic substitution cipher
14:
59:. The term "crib" originated at
51:). These can be used to reveal
1:
558:Geggel, Laura (29 May 2019).
522:, Harmondsworth: Allen Lane,
359:Geggel, Laura (29 May 2019).
485:, edited and translated by
394:. New York: Arrow. p.
263:Cryptanalysis of the Enigma
720:
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511:, 1984, pp. 241–45.
193:, which assumed that "
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21:known-plaintext attack
699:Cryptographic attacks
334:Lee, Loyd E. (1991).
227:to change his plans.
211:systems, such as the
147:At Bletchley Park in
487:Christopher Kasparek
283:Ultra (cryptography)
278:Polish Cipher Bureau
268:Kiss (cryptanalysis)
454:, 1984, pp. 243–44.
505:Władysław Kozaczuk
479:Władysław Kozaczuk
448:Władysław Kozaczuk
225:William Halsey Jr.
138:Qattara Depression
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641:Chosen-ciphertext
551:978-0-19-284055-4
538:Copeland, B. Jack
238:Classical ciphers
221:the world wonders
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191:Eins Catalogue
142:"Heil Hitler,"
129:Bletchley Park
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63:, the British
61:Bletchley Park
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391:The Code Book
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567:. Retrieved
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86:, p. 22
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671:Related-key
200:The Polish
179:Alan Turing
103:translation
53:secret keys
693:Categories
473:References
430:3540200207
118:ciphertext
57:code books
49:ciphertext
43:) and its
39:(called a
676:Known-key
651:Lunchtime
569:31 August
370:31 August
165:gardening
157:North Sea
47:version (
45:encrypted
37:plaintext
646:Adaptive
634:Adaptive
518:(1982),
388:(1999).
307:, p. 78.
273:PC Bruno
252:See also
75:—
72:solving.
27:) is an
540:(ed.),
320:, ed.,
93:History
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526:
509:Enigma
493:
452:Enigma
427:
402:
342:
134:Wetter
125:Enigma
289:Notes
258:Cadix
213:5-UCO
161:mines
159:with
111:Greek
107:Latin
99:slang
84:(PDF)
571:2020
546:ISBN
524:ISBN
491:ISBN
425:ISBN
400:ISBN
372:2020
340:ISBN
232:KL-7
230:The
195:eins
183:eins
55:and
41:crib
31:for
19:The
611:in
396:184
109:or
25:KPA
695::
562:.
507:,
481:,
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398:.
363:.
303:,
601:e
594:t
587:v
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23:(
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