THE Charles I cipher, after which this department's problem No. 199 was modeled, is only one of several ciphers of the same type employed by this monarch. And, fortunately, knowing the exact type beforehand, it is one in which it is an easy matter to determine the key.
To solve this cipher it is first necessary to distinguish between the numbers used for the alphabet and those used for the vocabulary. Letter symbols can then be determined by alphabetical approximation and frequency, and word symbols by context and location in the vocabulary. To illustrate these steps more clearly. Cipher No. 199 is reprinted herewith:
55. 29. 91. 26. 73. 44. 54. 71. 88. 41. 76. 30. 43. 57. 82. 59. 12. 58. 63. 85. 38. 25. 74. 52. 14. 55. 79. 77. 28. 18. 73. 26. 86. 109. 17. 61. 57. 19. 27. 11. 49. 135. 142. 122. 42. 56. 81. 75. 89. 80. 84. 25. 23. 136. 149. 86. 37. 60. 87. 35. 39. 64. 76. 28. 78. 77. 30. 21. 16. 62. 83. 36. 108. 92. 40. 58. 24. 103. 13. 54. 34. 29. 75. 136. 74. 27. 90. 24. 10. 50. 124.
A frequency table of these numbers will show that there are only a few breaks from 10 up to 92. Also that numbers above 100 are sparingly used, there being, in fact, only nine different numbers between 103 and 149, inclusive.
This can be taken as meaning that these higher numbers probably represent the vocabulary terms, and the lower numbers the letters of the alphabet. Proceeding on this assumption, at any rate, a trial alphabet can now be constructed by adjusting the numerical series, 12 to 92, to the letters A to Z.
This should be done so that the gaps in the series will come opposite letters of low frequency, such as J, K, O, X, and Z, and repeated numbers opposite letters of higher frequency. The number of symbols assigned to each letter should roughly agree with alphabetic frequency. Here, 45 to 48 would be placed with J and K; 65 to 70 with P and O; and from 93 up, with X, Y, and Z, as shown below:
A 10,11,12,13,14 N 57,58,59,60 B 15,16,17 O 61,62,63,64 C 18,19,20 P 65,66,67 D 21,22,23,24 Q 68,69,70 E 25,26,27,28,29,30 R 71,72,73,74 F 31,32,33 S 75,76,77,78 G 34,35,36 T 79,80,81,82,83 H 37,38,39,40 U 84,85,86,87 I 41,42,43,44 V 88,89 J 45,46 W 90,91,92 K 47,48 X 93, etc. L 49,50,51,52 Y M 53,54,55,56 Z
In testing the accuracy of the trial alphabet it is best to start with short sequences which are preceded and followed by vocabulary numbers, since such sequences will more than likely represent single words. Three short sequences occur at the end of the present example, marked off by the numbers 108, 103, 136, and 124.
Numbers in the trial alphabet will probably be off one or more letters one way or the other. Hence, it will be necessary in deciphering to try a given number for a few letters before and after that for which it is tentatively listed. Here, for example, the following sequence will be found to signify REVEAL, as indicated in italics.
74. 27. 90. 24. 10. 50. P C U B J Q D V C K R E W D A L S F X E B M T G Y F C N
By correcting the trial alphabet to conform to each newly deciphered word, it becomes more accurate as decipherment proceeds, and the translation less difficult. Having deciphered the literal part of the cipher, the vocabulary numbers can usually be determined by context alone.
Thus it is obvious here that 103 equals AND; and so on. The translation in full of this example, with vocabulary equivalents in italics, is as follows : "Never inquire into another man's secret but—109—conceal that which is—135-142-122—intrusted to you—136-149—though pressed both by—108—wine and—103—anger to— 136—reveal it—124."
Another method of solving this type of cipher will be described in the next issue of this department. In the meantime try Cipher No. 202, which is of the same type as No. 199, but uses a much shorter key. Once you get started on a cipher of this kind it is an easy matter to follow up the lead.
Perhaps the easiest start in last issue's crypt, No. 197, is found in WXIZMJJK, which, with J as e from its high frequency, suggests the suffix -teen, with fourteen as a good guess.
This would check with BXI—you, LXIMY—south, and so on. The answer: "Camped just south long bridge across Myakka River fourteen miles east Myakka City. Wait until you come." There is only one unusual feature in this text, the "kk" in "Myakka." Did it stump you?
To decipher No. 198 you had only to read the fifth word of every sentence. The message: "Avoid the suspicion of evil." Easy enough when you know how!
Our opening cipher this week is a simple substitution cipher. Mr. Walker has doped out a sentence of all long words.
In No. 201 Mr. Roe has used a 1-to- 26, A-to-Z, alphabet in conjunction with a ten-letter key word which represents the ten digits. To encipher any letter, substitute for it the key letter or letters indicating its place in the alphabet. With the key word HYDRAULICS, for example. A, the first letter of the alphabet, would become H in cipher; T, the twentieth letter, would be YS; and so on. Letters not in the key word are used as word spacers. Find the key!
Get as many answers as you can and send them in.
Keep your new ciphers coming right along, too.
CIPHER No, 200, by M. Walker, Akron, Ohio.
VEBSABYE, VETYWD, UIEYNKUW NZKSCYNYV. TVUIX BSKNIVE- COPV, OCTYBXNCTVSD BEENQKE- NW VOBSUIX UTBOONVVURSN JUQBSBDBI JNUXJEV.
CIPHER No. 201, by Charles E. Roe, Hudson, Massachusetts.
AEXLL ELRUK OUUEU BCLBJ SLMET UMCUK ASRLA LLBUK CMGLK LEULL ALBEU ELCQA CBBEL BPUUE VLJUL CEUKH URELL UPOOT
CIPHER No. 202.
18.35.33.42.20.48.44.23.38.22.37.45.21.32. 18.49.51.32.45.31.21.38.26.18.16.30.36.30. 15.18.20.57.64.46.34.18.16.17.45.30.15.38. 49.15.39.22.44.25.38.22.21.23.16.18.43.34. 39.41.57.64.19.20.42.21.39.31.26.33.16.42 27.35.33.61.47.35.39.19.41.49.31.17.34.30. 41.57.44.25.26.40.43.49.36.22.61.18.27.36. 25.21.38.