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IntroductionFriedman, after finding the wiring of the rotor in position V, tackles message decryption. The problem is more simpler than before: each cryptogram can be broken down into a series of simple substitutions limited to 26 letters. Solving a simple substitution is easy for an amateur... if it is more than 150 characters long. On the other hand, even for an expert like Friedman, deciphering limited substitutions to 26 letters is a real feat. Even if, in theory, Friedman was able to decipher all the messages in this way, he preferred to continue to reconstruct the wiring of the other rotors, which allows find the plain text of messages more easily and show the Navy that Hebern's machine no longer has any secrets for him. A series of simple substitutionsFriedman, using the interval method, finds the wiring of the rotor in position V:
D P G T B Z O H R Y M S L A J I W C K U Q F N V X E
He is therefore able to removing from the cryptogram, the action of the Lampboard permutation as well as the action of the rotor V (we call this result c'). He obtains, for the first message, the following result: C:\H5_TOOLS> more ROTORS\N5.rot DPGTBZOHRYMSLAJIWCKUQFNVXE Rotor 5 Navy C:\H5_TOOLS> python hebern5_tui.py -I 0:0:0:0:N5 -E AGRRAAM -d ^ < CHAL1924\msg_01.cry QKZWDEZQJLYJPZNQDJZEWJOJZWDBGMTCTMABTANMLEHLLOCEMVMEABATKVNUIBIA MBNZAMUIDATGNZGCBSUNUXPKBPUENOQNUOQYCBFBXRKHUAAUHDYZKTGXACXCUGZR JDZPCQCNTQZOQUJQQOENYQOYTOUFPUNCXOVFVQTAFYYFTRXDHTRXYIXONLKNEONA YNJYIGWTYWROUSNALGSIKRVGCQKCTCJPCWBWCZJWZQHBMWFJDWTFBABDWFIHJRRJ VBMNLLILDBOLAWCEFKVEFDFGNEAKABJRTTFRVXWLNFVKONWRTFYRAFPVPGNVDPUN RPRUAVDPUNWe reorganize the decryption by having for each column, a particular position of rotor V: Crypto J c' Q Crypto N U T X H V Z S L U M L Z X H X H O H Y B R C L M S c' K Z W D E Z Q J L Y J P Z N Q D J Z E W J O J Z W D Crypto U F C D S U F M O V K C N K Y N N G A U W Y L I Q Z c' B G M T C T M A B T A N M L E H L L O C E M V M E A Crypto U T L W B Y D G O W K H R X T C J C S V G J J F Y V c' B A T K V N U I B I A M B N Z A M U I D A T G N Z G Crypto J S R C E Z U Q K D O Y T X V T V C A S N Q P G E C c' C B S U N U X P K B P U E N O Q N U O Q Y C B F B X Crypto A R U C W L D D C U Q D X F L C B K D B E C H X D G c' R K H U A A U H D Y Z K T G X A C X C U G Z R J D Z Crypto V A Y E E U Z H W R W V V P V D V M G E N J W V U U c' P C Q C N T Q Z O Q U J Q Q O E N Y Q O Y T O U F P Crypto E N M O Q J P U M V K G W Q C Z W K R I I X M J A C c' U N C X O V F V Q T A F Y Y F T R X D H T R X Y I X Crypto L N S W E A M I A U U V W V B L E M B O S P X F R R c' O N L K N E O N A Y N J Y I G W T Y W R O U S N A L Crypto S G O W C J L V M H Y A J E Z G F Y B U D A Z L O Q c' G S I K R V G C Q K C T C J P C W B W C Z J W Z Q H Crypto U M T Z T O V T B D K W H A C H Y N Y O B N P I H R c' B M W F J D W T F B A B D W F I H J R R J V B M N L Crypto T K S X F G W M N L N G O H Y M K H P G W I E B E L c' L I L D B O L A W C E F K V E F D F G N E A K A B J Crypto A B L Z C J U C L J X S O U D L W U T A F I A R T U c' R T T F R V X W L N F V K O N W R T F Y R A F P V P Crypto S N G X A Z B O H G W P Y G Z R V c' G N V D P U N R P R U A V D P U N Deciphering the first line
Friedman tells us in his report:
Crypto J --- N U T X H V Z S L U M L Z X H X H O H Y B R C L M S
7 522 819 5182316172321 51818 823 51922231523 522 8
Plain P --- r e s i d e n t o f t h e n n i t e d s t a t e s i
(U)
Notes:
Decryption of other linesThe hardest thing is done. As soon as we have deciphered the first line, it gives information to continue, for example cribs (UNITED STATES). Friedman tells us that for the second line begins with a word starting with "i". According to him, the second letter is almost certainly an “S” or an “N”, possibly a “D”. Finally he finds "INVITATION" (which provides a new Crib). So, if we inspect the complete solution of all messages, we see that several words are used several times: "UNITED STATES", "PACIFIC", "JAPAN", "JAPANESE", "BRITISH", "INVITATION", "ZEPPLIN COMPANY", "DEPARTMENT", "GERMAN", "GOVERNMENT", "GERMAN GOUVERNMENT", "WAR SHIPS", "BATTLE SHIPS", "VESSELS", "CRUISERS", "NAVAL", ... The ATION pentagram is very common. Thus, in the tenth line of the crytogram, we can easily place the word "INVITATION".
G S I K R V G C Q K C T C J P C W B W C Z J W Z Q H
i n v i t a t i o n
G S I K R V G C Q K C T C J P C W B W C Z J W Z Q H
i i i n v i t a t i o n t o
It seems at first glance that we are far from the solution.
In fact the letters that remain to be found are not those
already found, this reduces the possibilities. On the other
hand, the doubled letters (G and K) undoubtedly correspond
to frequent letters. One of them is probably the letter "E".
In any case, Friedman deciphered the following lines, and thanks to them, he was able to find the wiring of the rotor in position I. Crypto J c' Q Plain P Crypto N U T X H V Z S L U M L Z X H X H O H Y B R C L M S c' K Z W D E Z Q J L Y J P Z N Q D J Z E W J O J Z W D Plain R E S I D E N T O F T H E U N I T E D S T A T E S I Crypto U F C D S U F M O V K C N K Y N N G A U W Y L I Q Z c' B G M T C T M A B T A N M L E H L L O C E M V M E A Plain N V I T A T I O N T O D I S C U S S P A C I F I C O Crypto U T L W B Y D G O W K H R X T C J C S V G J J F Y V c' B A T K V N U I B I A M B N Z A M U I D A T G N Z G Plain C E A N P O L I C I E S C O M E S L I K E A B O M B Crypto J S R C E Z U Q K D O Y T X V T V C A S N Q P G E C c' C B S U N U X P K B P U E N O Q N U O Q Y C B F B X Plain T O J A P A N W H O W A S P R E P A R E D T O C O N Crypto A R U C W L D D C U Q D X F L C B K D B E C H X D G c' R K H U A A U H D Y Z K T G X A C X C U G Z R J D Z Plain S I D E R R E D U C T I O N A R M A M E N T S B U T Web Links
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