Sketcher. The Transmission of Secrets.

Waikato Times, Volume XXII, Issue 1836, 12 April 1884, Page 5 (Supplement)

Sketcher. The Transmission of Secrets.

The reader Las, no doubt, frequently heard of letters or telegrams, containing private information of an important kind, being -written in cipher, and has probably -wished to know something of the nature of this system of writing. We shall, therefore, endeavour to satisfy this laudable curiosity by explaining a few of the many methods that have been in use from time to time. The earliest system of cipher-writing, and the simplest, is easily explained, and merely consists in transposing the letters of the alphabet. Thus, instead of taking a; as the first letter of the alphabet, i might be taken, and if so taken would stand for a ; c would then stand for J, d for c, and so on. Of course any letter agreed upon by the correspondents may bo taken for the first — m t for instance, may be taken for a, when n would be b, and I would be z — the last letter of the alphabet. The key to a cipher of this kind lies in knowing what letter is taken as the j initial letter. Suppose we take das our i initial letter, and express the message, "Come at once," in this cipher. The easiest way to do so is to write the letters of the alphabet, beginning with d and ending with c, in ono line j and below this line to write the alphabet in its natural order, putting a below rfj b below c, &c. Taking our message now, we havo first the letter c ; it stands below f ; therefore, f will take the place of c in the cipher ; 0, being below r, is discarded for that letter. Proceeding in this way, we arrive at the barbarous and foreign looking form — " Frph dw rqfh." This cipher, as we have said, was the earliest used, at least the earliest that we have any record of, and was adopted by Julius Cajsarand his successor, Augustus, the former taking d as his initial letter, and the latter c. An instanco of its use also occurs in the twenty-fifth chapter of Jeremiah, where Sheshaoh is written for Babel — in this case, of course, the reader must remember that the Hebrew alphabet is employed. Another method easy enough to explain, but impossible to decipher, is for each correspondent to have a book — say a certain edition of Shakespeare — the pages numbered exactly alike, and the same number of lines on each page. Then a message may be sent in the form of figures, representing the place of the words of the messsgo in the book. The first number represents the page, the second the line, and the number of the word from the beginning of the line. In this way every word in the message would require three numbers. If the words of the message be all taken from one page, however, and eacli word be indicated by a number expressing its position from the first word on the page, then ono number is quite sufficient for each word. Thus, taking Addisons Spectator, page 112, the message, " I am very well, and think it best the people meet the whole week," would be written : — 112. 1, 2, 4, 11, 24, 28, 80, 37, 48, U, 114, 115, 116] Somo time ago there fell upon the writer's eye this advertisement: — "Two John — I at Monday will Cross evening meet street at you on seven." Now, to put a secret in that form is the very height of simplicity j anyone with the slightest knowledge of cipher-writing can read it at once. It is evident that the word " street " should read immediately after the word " Cross." If the advertiser had put a small c instead of a capital, it would not have been so bad ; even then, however, it would be apparent euough. Once we have discovered that "street" should bo read immediately after " Cross," we have the key. Thore are j two words between " Cross " and " street," therefore write the message in this way : — I will meet yon at Crops street on Monday evening at seven. Now read along the top column, then the second, and then the bottom one. The "Two" with which the advertisement begins is to give the number of words between the successive words. This kind of cipher was used by the Earl of Argyle in his conspiracy against the Crown. Charles I. wrote in cipher, and we have some of his letters to his son, which have been deciphered. He used a numeral cipher, which we may illustrate by an example. Let the number 231 be the key, and let us throw this message into cipher :-~ 23 123 123 123 1 231231 23 1 231 Imprison tlie leaders at once. Begin by writing the key number j£ tfie manner indicated, a_sgure~abbvo each letter. htijovS^'tftrffret letter, we find the figure 2, which means that instead of i we are to use the second letter from ii — that is, k ; in, the next letter, has 3 above it, we therefore substitute for m the letter p. Going on in this way, we get the heterogeneous mixture, " kpqtltqq ujh mgdegut cw ppff." The recipient of these outlandish words applies the key number, 231, putting the 2 above Jc, 3 above p, &c, and thus restores the message to an intelligible form. In this cipher the reader will observe that the same letter may do duty for different letters. The word " once," for instance, containing four different letters, becomes in the cipher " ppff," where we have only two different letters — the reason is abvious. Such a cipher is pretty safe for a short message j for a long message, however, it is as open as plain English to a man skilled in deciphering. We shall explain two other methods, reminding the reader, however, that there are a great many more. Take first a numeral system :—: —

This table is the key, a copy of which is kept by each of the correspondents. A message is thrown into this cipher by replacing the letters with the numbers above and at the side of each letter — the former preceding the latter. Thus/ would be written 21 ; m, 32 5 s, 43, &c. The word " escape " would be represented by the numbers 15, 43, 13, 11, 35, 15. Instead of the numbers 1, 2, 3, 4, 5, any others wilLdo ; on© must know these numbers to decipher a communication in this form. A more secret method than any we hare as yet touched upon is what is known as the square cipher. In this case each party has twenty-six alphabets, placed one under the other in the form of a square, thus :—

A key -word is now agreed ujpon, and in this lies the virtue of the square cipher ; for any combination of letters will answer this parpose. Suppose we take " geda "as our key, and express the words, "idea," "beach," and " bed" 5 write the key- word over these words in this way :— peda gedttg ecU idea beach bed ( i is the first letter, and the key above it is q j i therefore we look in the table for the line be- [ ginning with t and the column beginning with

g. The line beginning with %is the bottom one in our eiample, and the column beginning with q has oin this line ; o, therefore, is the letter we are in quest of. Our second letter is d, above it is c. The line beginning with d and the column beginning with c intersect in h, which is to take place of d. In this way these three familiar words, " idea," " beach," and "bed," take on the Gaelic-looking aspect — " ohha hiden fhd." From this example the reader will doubtless see clearly enough how to work the squaro cipher. To find the intersection of the column and the line, a square card may be used ; this renders the operation of more speedy performance. Formerly this kind of writing engaged the attention of men to a greater degree than at the present day. The fact is, there are not so many secrets now-a-days as there used to bej the majority of people are busy with work of an honest kind, and they have very little time to write even in plain English, let alone the laborious cipher. Indeed ordinary writing is beginning to prove rather slow for this electric age, and many people now find it necessary to resort to shorthand. — CasselFs Magazine.

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