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SOLVING CIPHER SECRETS E d i t e d by M . E . G h a v e r
PRESENTING T H E " M I X E D " DIGRAPH T E S T FOR SOLVING A TRANSPOSITION CIPHER—AND SOLUTIONS TO No. 70 AND T H E BOOKKEEPING CIPHER OF SEPT. 17
IN last week's installment on solving the type of transposition cipher described in the issues of September 17 and 24,
certain key lengths in cipher No. 73—reprinted below—were eliminated by factoring; and certain letter combinations were mentioned as probably occurring in the message.
T V Y I E T R R O R E H N I A E U D S R l E O N I O R E N A E E O R P T E A L O L T S U H L H Q N O U C A D D C S A A E T D V F U G N N Y C Y I
T h e probability of these or other combinations may be tested by examining the digraphs formed by juxtaposing various letter sequences of the cryptogram.
A method for determining this relative " compatability " by digraph frequency has already been given i n the J u l y 3 , 1926, issue. So another method wi l l be presented here, the " mixed " digraph test, based on the fact that the consonant-vowel—CV— and vowel-consonant—VC—digraphs, together, average about sixty-five per cent of all digraphs i n straight Engl ish text. (Note: B y the J a n u a r y 23, 1926, table of ten thousand digraphs, V V = 5 . s % ; C C = 2 9 . 4 % ; C V = 3 2 4 % ; V C = 3 2 . 7 % ; total, 1 0 0 % . )
T h e " mixed " test is much more rapid than the " frequency " test, although probably not so accurate. Nevertheless, it is a valuable adjunct to the latter, and is also quite worthy of being used on its own merits. F o r example, it points unerringly
to the correct Q U combination in the present case, as shown below, where series of letters containing Q and V have been matched to bring the QU's together. These test sequences, here consisting of seven letters, may be made of anj^ length.
H I CV H L H Q H D L A CV L T L N L V H E CV H S H O CV H E
*ou * Q U * Q U * Q U N D N H N C N G O S V C O L V C O A O N V C U R V C U H V C U D V C U N V C
S 2 2 2
T a k i n g the first of these combinations as most probable, since i t gives a larger and more nearly normal C V - V C count than any of the others, the next step is to find the i n terval between the two series of letters H L H . . . and l A E . . .
A n y digraph in the column may be selected for this purpose; and in counting the interval, it does not matter which letter of the digraph comes first in the cryptogram. F o r example, Q is the forty-eighth letter of this cryptogram, and the above U is the seventeenth, giving an interval of thirty-one letters.
Other intervals could be found by simi lar ly matching other series of letters. B u t they are unnecessary i n this case, as subsequent articles of the series w i l l show. H o w to use the interval, 3 1 , in the further elimination of key lengths wi l l be explained next week.
L a s t week's simple substitution cipher
640 F L Y N N ' S W E E K L Y D E T E C T I V E F I C T I O N
N o . 74 conveyed the message: " J i m : T e l l the boys to meet me at the foot of Canal Street to-morrow night. No one is wise to our plans. B i l l . " T h i s cryptogram should have readily yielded b y taking E I D as the, and then by substituting through such groups as F Y — t o , C Y Y C D — w o owe, E D A A — t e l l , and so on.
Cipher N o . 75 used the subjoined simple adaption of the athbash alphabet—iee September 3 issue. A n interesting method of varying this alphabet by means of key words was illustrated last week i n the explanation of cipher No. 71 .
A B C D E F G H I J K L M Z Y X W V U T S R Q P O N
No. 69 ( M y e r S t i n e ) , the " bookkeeping cipher," published three weeks ago, used an alphabet of dollars and cents. Application of the system is illustrated by the accompanying decipherment of the first column. T h e message: " Simplicity is a ready mask for artifice." M r . Stine, you may remember, wanted to test the " seaworthiness " of his " craft ." D i d vou sink it?
A B C D E F G H
I J
K L M
13-31 z 12.21 Y I I . u X 10.01 W g.90 V 8.80 u 7.70 T 6.60 S S-So R 4.40 Q 3.30 P 2.20 O 1.10 N
Store, No. i
.?o.6o S-oo 1.30 2.00 S-oo
11.00 5-70
.21
S30.81
- S I -
M P L -I -C -I T - Y
No. 70 (Charles P . W i n s o r ) , also published i n the September 17 issue, used the key word L E X I N G T O N in conveying the message: " Transposition ciphers have not received their fair share of the attention of cryptographers." T h e set-up was as follows:
L E X I N G T O N 4 1 9 J 5 2: 8 7 6
H A N S I O N C
O S I P H E
H A V E N O T C E I
I R F A I R E O F T H
A T T E N T
E D T S E
I O N O F C R Y P T O G R A P H E R S
T h e number of letters in this cryptogram, 79, balked elimination of key lengths b y factoring. B u t the cryptogram is not proof against other methods of attack being outlined in the current series of articles on this type of cipher. L a s t week's suggestion that the word C I P H E R was in the message should have given you a big l i ft .
I n submitting No. 77, this week's s imple substitution cipher, M r . Dockhan suggests that we have some funny messages for a change. T h i s is a good idea. Decipher M r . Dockham's example, have a good laugh, and fix up a funny one yourself. There is something i n this world besides being altogether serious.
No. 78 is another transposition cipher of the same type as No. 70. A n d finally, No. 79 employs the Vigenere square, or equivalent apparatus, but without a k e y word, the key letters being scattered throughout the message and enciphered with the text. T r y " running down the alphabet " on this cipher. (See November 13, 1926, issue.) A n d then try to fathom M r . Cooke's method of handling his k e y letters.
C I P H E R No. 77 ( J . A . Dockham, Oakland. Cal i f . ) .
U G U G Y U Z I G A T O S U G S U G Z O K O S U G Y U G G I E G P O S U K K A W U D I X U G O V Y K U B U A K I X U G Y A R E O B U G Y N U G S U G U D D I J U G P O I X Y U A G Y O S P U G S H P U G N Y I Y M O W A D D U Z O S E L B M O U B .
C I P H E R No. 78.
O T E N S L I N R T A D O W A A Y T I E T T H A B E
H I E N U C D E M M
C S D A E V T T A S
C I P H E R No. 79 ( W . A . Cooke, Montreal, Quebec, Canada).
H A O G W T Q G P O Z S X V S U J M G G X G B S H O E J X P D R E C N M V Z B W N B P H N J G T I E Y F A S I T Z J Q F Q S P C D
L E T K K F H E T F S H F N T D H N U E
Ciphers Nos. 77 and 78 wi l l be fully explained next week, and No. 79 in three weeks. T r y to solve them, and send in your solutions. W e would like to see more answers to the more difficult ciphers pouring in . .A,re you finding them too hard?
Don' t forget, fans, to include translations and explanations with ciphers submitted for publication.
10 F W
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