SOLVING CIPHER SECRETS E d i t e d by M . E . O h a v e r

IN WHICH IS APPLIED A METHOD EXPOSING T H E VULNERABLE SPOT IN LAST WEEK'S DOUBLE TRANSPOSITION CIPHER No 115

TH E vulnerable spot in last week's double transposition Cipher No. 115 is due to the fact that the message

assumed the form of a square when set up for encipherment, and that, consequently, it became subject to the easy method of resolution described in some detail later in this article.

I t is possible for squares to occur in the system under discussion only through the use of keys of improper length, or through failure to add the necessary nulls to mes­sages which are not multiples of five letters in length. A message of thirty-six letters with a key of six letters, for example, would make a six by six square if the four nulls were omitted. T h i s can easily be seen b y any one.

When communications are in multiples of five letters, on the other hand, squares are only possible with keys of 5, 10, 15, 20, or any other multiple of five letters. T h u s , Cipher No. 115 used a key of ten letters with a message of one hundred let­ters, resulting naturally in a ten by ten square.

Application of the present method wil l be illustrated with a five by five crypto­gram, formed by using the key, T O W E R — 4-2-5-1-3—as shown herewith in encipher­ing the message, S E N D R E E N F O R C E -M E N T S A T O N C E — A . T h e final A of this message is the nul l required to fill out

the multiple of five letters, tration follows:

(a)

T h e illus-

(0

T 0 w E R 4- 2- s - 1 - I S E N D R E E N F 0 R C E M E N T N A T 0 N C E A D F M A E E E C T N R 0 E T A S E R N 0 N N E S C A T T N S F E 0 E N E N A 0 C D E R S N M C E R E

A glance at this encipherment wi l l show that the whole lines of the message (a) form whole columns of the first transposi­tion (h), the letters in al l of these columns being similarly transposed. Further, the columns oi (b) are preserved intact in the lines of the second and final transposition (c), only being changed in their order.

Hence, to decipher an example of this k ind it is only necessary to transcribe the cryptogram by horizontals, left to right, into a square of the proper dimensions, and then to rearrange the columns thus formed so as to develop message sequences, words, and so forth, in all of the lines.

I f the columns of the square are num-799

800 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

bered in serial order, this rearrangement w i l l also recover the numerical key, as shown at (d), where the key 4-2-5-1-3 is revealed. T h e whole message may then be read by taking the several lines in the order indi­cated by this key, and dividing into words.

4 - 2 - 5 - 1 - J (d) N T S A T /

E E N F O a O N C E A 5 S E N D R 4 R C E M E 5

A s in many types of transposition c i ­phers, paper strips may here also be used to advantage. F o r example, there would be five strips in this case, each bearing a num­ber and one of the above columns of five letters.

L a s t week's No. 115, in the same way, would require ten strips of ten letters each; and so on. T h i s method is not at a l l diffi­cult. I n fact, it is great sport to t ry various combinations of columns or strips, and watch the message develop before your very eyes.

I f you don't believe it , t ry N o . 118, here­with , where the square results from the supposedly inadvertent omission of the nulls required to fill out the multiple of five letters. Also, if you have last week's issue handy, and you haven't already solved No. 115, t ry to get the solution by this method. T h e answer to N o . 115, by the way, was promised this week; but on second thought, and for evident reasons, i t w i l l be better held over until next week.

Here is the solution to last week's " Q . and A . " Cryptogram No. 113 (Anthony R a n i e r i ) , Question: W H O S A I D , " I T I S A C O N D I T I O N T H A T C O N F R O N T S U S — N O T A T H E O R Y " ? Answer: G R O V E R C L E V E L A N D . T h i s one should have quickly yielded to solution by inspec­tion.

T h u s , the single letter J , occurring twice, was probably A. Substituting this i n H F J H , the first and last letters of which are alike, would give THAT. After which R H would become IT, and R Q , IS. Sub­stituting known values in Q J R P would give SAI-, obviously SAID. A n d so on. F o r another brain teaser of this sort t ry Cipher No. 116, herewith.

L a s t week's transposition Cipher N o . 114

( A r t h u r B e l l a m y ) expressed the message: " W E Q U I C K L Y Q U E S T A S Q U A R E . N E X T , A ' Q ' U S E D A S A C L U E , A S ' Q ' U S U A L L Y F O L L O W E D B Y ' U , ' S O L V E S Q U I T E Q U E E R Q U I Z . "

Encipherment was performed by writ ing the message by horizontals, left to right, into a nine by nine square, as shown herewith, and then by taking the columns downward in the order indicated by the numerical key 4 - 7 - 1 - 2 - 6 - 5 - 8 - 3 - 9 , derived from the key phrase Q U E E R Q U I Z .

Q U E E R Q U I Z 4 - 7 - 1 - 2 - 6 - S - 8 - 3 - 9

W E Q U I C K L Y Q U E S T A S Q U A R E N E X T A Q U S E D A S A C L U E A S Q U S U A L L Y I S F O L L O W E D B Y U S O L V E S Q U I T E Q U E E R Q U I Z

I n many transposition ciphers a Q U com­bination is a ready-made clew. B u t this one contains so many Q's and U 's that i t is hard to tell which are in combination. T h e nine by nine square, however, quickly settles the matter. F o r columns of nine let­ters bring most of these Q's and U's to­gether.

Before exposing you to the devastating fire of this week's ciphers, there is yet an­other of them. No. 117, that requires some comment. M r . Napier has based this on the well known Vigenere table of twenty-six alphabets, using numbers instead of let­ters. More we cannot tell you without spoiling the problem.

CIPHER No. 716. Question: OQFY BE F UFGMXBCYQ? Answer: G OZGLQ SHZZ ES CDFJC-

LGFQ RCDPCDVA RWCLW JQDPQJ OF PCSSCLHZF F E SCDP FWQ R G I KQFRQQD FWQ QDFJGDLQ GDP LODF-JGZ LEBOGJFBQDF.

CIPHER No. 117 (P. A. Napier, Louisville, Kentucky).

14- 19-19-10-10 16-16-20-20-3 3-25-25-22-22 21-21-2-2-2 2-20-20-25-25 7-7-26-26-23 2 3 -i o - i o - S - 5 15-15-26-26-7 7-10-10-13-13 15-15- 26-26-8 8-15-15-13-13 8 - 8 - 2 6 - 2 6 - 1 5 15-18-18-7.

CIPHER No. 118. SREAN KDSPA ESTTY METNA USEDM HNTEE E E R Z E J RENT ATRSO OTGTU RRTSF AFORC EVRO

M F W