IN reconstructing the key to cipher No. 44 ( J. McA. T.), which was published at full length in the July 16 issue, and as below with a description of the system in the length of the groups.
Message: IWOND ERWHE THERT Cipher: VZPOD BWEZL WBTLO HESIM PLEAN DDIRE CTMET ACXPC PRHGE GBVXN QMMMD HODOF ENCIP HERME NTHER ZYXTF RCGKS AVIYE OAEXY EUSED ISREA DILYD ISCOV ICGHD IBHUK KLDLO IUICT ERABL EITHI NKNOT BALAE BWEQS NZFET
Given the translation, this is easily done by factoring intervals between recurrent message groups which give rise to repeated cipher letters at respectively similar intervals in the message and cryptogram.
Here, for example, ER occurs at the sixth and seventy-sixth letters of the message, producing B's in the cipher, with an interval of seventy in both cases. Similarly, HE, at the sixteenth and forty-sixth letters, and the resultant A's, both occur at an interval of thirty letters. The only odd factor in common to these two numbers is 5, indicating groups of that length in encipherment.
Dividing into groups of this length, letters having the same units in common may now be discovered by comparing message and cipher letters in each group. In the first group, for example, the first units of the letters I, O, and D—message—are the same, respectively, as the first units of V, Z, and P—cipher. And the second units of I, O, and D are the same as the second units, respectively, of P, 0, and D—cipher.
By treating all the groups in this way, and placing letters with the same first units in rows, and those with the same second units in columns, the following tabulations are obtained:
(Rows) (Columns) I V B E R I│E│T│M│W O Z H N A P│L│O│C│Z D p G Y K X│G│D│K│R T W M X F S│N│V│A│Y S C Q U L H│F│Q│B│U
It is now possible to combine these squares into one, by rearranging the letters in the rows and columns. In doing this, observe that only the order of the letters in any row or column is changed.
(Reconstructed Key) (Original Key) y x v w z 1 2 3 4 6 v I V B E R 1 G D K Y P w P D K G Y 2 F T M W X x X T M F W 3 E V B R I y S Q C L U 4 N O A Z H z H O A N Z 5 L Q C U S
Assigning the values v, w, x, y, z, to the rows, the next step is to find the values for the columns. And this may be done by finding letters which have the same units in first and second places. Groups of the present length afford four such points of comparison.
In the first group, for example, the first units of W and N—message—are the same, respectively, as the second units of V and Z—cipher—thus fixing the values x and z, respectively, for columns two and five. Similarly, the second units of W and N are the same, respectively, as the firpt units of O and D—cipher—fixing the valuess and w for columns five and four. The other values may be found by the same method.
A given key in this cipher can be transposed in fourteen thousand four hundred different ways, and yet give identical results in use. Note here, for example, that our correspondent's key—arranged in square form—and the reconstructed key produce exactly the same cryptogram.
(Reconstructed Key) (Original Key( I W O N D I W O N D v x z z w 3 2 4 4 1 y z x w x 5 4 2 1 2 V Z P O D V Z P O D
Without the translation, group lengths could be determined by analyzing intervals between letters or series of letters. And predominating letters would be those using predominating units. Here, for example, the predominating unit 3, used forty-five times, occurs in five out of six of the predominating letters, E, B, A, C, I, L. Positions of letters in groups could also be turned to account.
Did you get No. 56, last week's "question and answer" cryptogram? Here is the translation:
Question: What is the portrait parle, or speaking portrait system? Answer: This is a system of standardizing personal characteristics so that they may be accurately described in words.
No. 57 (F. H. Newell) conveyed the message: "I urge you to go away at once: you are in peril. " The keys were GO and PERIL. The alphabet was a straight A= 1 ... Z = 26, with & for zero. To encipher, first substitute numbers for letters of the message (a) and key (b); take the differences (c) between these numbers; and substitute letters, for numbers at (d).
(a) I U R G E Y O U 9 21 18 7 5 25 15 21 (b) P E R I L P E R 16 5 18 9 12 16 5 18 ——————————————————————— (c) 7 16 0 2 7 9 10 3 (d) G P & B G I J C
It is possible for some of the numbers to offer a choice of two letters in deciphering, depending upon whether the message number was larger or smaller than its key number by the given difference.
Now for this week's ciphers. No. 59 is another "question and answer" cryptogram. Two alphabets are used; one for the question, and the other for the answer. There are thus really two ciphers here, the solution to either one of which will help in solving the other.
In No. 60 you are being offered a fine example of transposition cipher. This is not too difficult; but be careful! Some traps have been laid for the unwary to stumble into!
No. 61 is based on a key sentence which must contain all the letters in the alphabet, the symbol for a given letter being merely the two letters before and after it. For example, with the sentence, "Pack my box with five dozen liquor jugs," A would be represented by PC; B, by YO; C, by AK; and so on. But in this case a much longer key sentence has been used, providing several substitutes for the frequently used letters.
CIPHER No. 59.
Question: KSOJ AT ABFGHJALM CMOTNBABR? Answer: SVC EBHQCFF HU BCDFHJ- KJM UBHZ D EDBS SH D IVHYC UBHZ EDBSKQOYDBF SH MCJCBDYF HB UBHZ SVC KJTKNKTODY SH SVC OJKNCBFDY.
CIPHER No. 60 (M. Walker, Akron, Ohio).
EDIIH NFCOR NAWLQ OESUS NCCEF TOENV RLCCI EEURN RNDSE EBIEV DYUOI ARFMQ QGNK
CIPHER No. 61 (J. Levine, Los Angeles, Calif.).
SQEIV METNO MNUBI KHEIK WUEEA SOTSX UBDZE TXUPR UDUDF HTEZS UDENF HASEN ADEIE POTNO TEJOO TUDOA TESQN OVMAS DZEIQ lEIHE LJFHB AVMEE IKSXO ATENM ADNOT EUCEI KOHEE IEIOT XUZS