Cipher

“ To use an image which I think will strike your poetic mind, let a cipher be what it may, immeasurable in size, written in gold, or written in pencil, it is only a cipher after all. A man of our times has said, “No zeal, above all, no zeal!” ”

“ While yet a school boy I had practiced with my playmates a simple system of a cipher; with this, which was the easiest form that I then knew for a basis, I worked out in the form of a letter, [198] that I could pass through to Baltimore on the blockade runners, a secret communication reciting my discoveries at Manassas, etc.
It is an easy matter to arrange a system of cipher communication between any two persons, which will be readily and perfectly understood by them alone, or only by those who have been furnished with a key. ”

“ CRYPTOGRAPHY (from Gr. κρύπτος, hidden, and γράφειν, to write) , or writing in cipher, called also steganography (from Gr. στεγάνη, a covering) , the art of writing in such a way as to be incomprehensible except to those who possess the key to the system employed. The unravelling of the writing is called deciphering. Cryptography having become a distinct art, Bacon (Lord Verulam) classed it (under the name ciphers) as a part of grammar. Secret modes of communication have been in use from the earliest times. ”

“ If a cipher seems to be a substitution cipher, the examining officer should look over the frequency of occurrence of each of the fifteen letters counted. If some letters (it is of no importance at present which ones) occur much more frequently than others and some occur rarely or not at all, we may safely decide on Case 4, 5 or 6 and let the clerk proceed to finish the frequency table for the message. ”

“ Substitution cipher presupposes the selection of a set of symbols which can represent the letters or words of messages. As to what these symbols may be, there is practically no limit; we meet substitution in our every-day life: the dots and dashes of the Morse alphabet, the pot-hooks of shorthand, the combinations of Braille, and so on ”

“ LESSON XV
The phrase “Biliteral Cipher” is made to contain the hidden word “key” by the use of a capital letter for the a form, and a small letter for the b form. The borders to the lines contain the cipher word “letter,” the blue sticks being the a form, the red ones the b form. The reading proceeds from left to right in each line, beginning with the line at the top. The children may be directed to cut out any set of letters of appropriate size to form any desired phrase, using capital and small letters on the same principle as in the example. ”

“ But, before leaving the simple for the complex, we must not overlook the celebrated key-phrase cipher, which discards the idea of multiple substitutes in favor of multiple originals! This cipher, shown in Fig. 79, is said to have been used for serious purposes. Its only difference from the ordinary simple substitution lies in the nature of the cipher alphabet, which must be a plaintext sentence, or phrase, containing the necessary 26 letters. The mysterious pronouncement, “One who has passed on is among us,” is the earliest example of which the writer has any recollection ”

“ After having decided that a cipher belongs to the transposition class, it remains to decide on the variety of cipher used. As, by definition, a transposition cipher consists wholly of characters of the original message, rearranged according to some law, we may, in general, say that such a cipher offers fewer difficulties in solution than a substitution cipher. A transposition cipher is like a picture puzzle ”

“ Cipher work will have little permanent attraction for one who expects results at once, without labor, for there is a vast amount of purely routine labor in the preparation of frequency tables, the rearrangement of ciphers for examination, and the trial and fitting of letter to letter before the message begins to appear. ”

“ The office work on a cipher under examination should be done on paper of a standard and uniform size. Printed forms containing twenty-six ruled lines and a vertical alphabet are convenient and save time in preparation of frequency tables. Any new cipher methods which are found to be in use by the enemy should, when solved, be communicated to all similar offices in the Army for their information. ”

“ Charles I of England is said to have used a cipher alphabet in which letters were represented by a series of dots, placed in certain positions with reference to the line of writing. An endless number of queer symbols is met with in fiction, such as the use of the little dancing men by Sir Arthur Conan Doyle. Cipher alphabets of the nature mentioned do not produce ciphers in any way different from those produced by substitution with letters and numbers ”

“ The whole cipher is so rationally exact that any one who knows the principle can make a key in a few minutes.
As I had gone on with my work I was much cheered by certain resemblances or coincidences which presented themselves, linking my new construction with the existing cipher. When I hit upon the values of additions of eight and nine as the component elements of some of the symbols, I felt sure that I was now on the right track. At the completion of my work I was exultant for I felt satisfied in believing that the game was now in my own hands. ”

“ Only that morning I had received a response from an expert in cipher—one of the officials at the Record Office in London—to whom I had submitted a copy of that tantalising document.
“This,” he wrote, “is what is known as the checker-board cipher, a numerical cipher invented by a Russian revolutionist some forty years ago, and of all secret means of correspondence is the most complicated and ingenious. It is absolutely undecipherable unless the keyword or words agreed upon by the two correspondents be known, and it is therefore much used by Anarchists and Revolutionists. ”

“ In cipher work it is necessary, under ordinary circumstances, to use any or all of the letters of the alphabet. To assist operators in keeping the text straight, it is customary to divide cipher text into groups of four, five, six or ten letters, and usually groups of five letters are used. The receiving operator may then expect five letters per group, and if he receives more or less he is sure that either he or the sending operator has made an error. ”

“ On what principle had these letters been arranged? He who held the paper was alone able to tell. With such cipher language it is as with the locks of some of our iron safes—in either case the protection is the same. The combinations which they lead to can be counted by millions, and no calculator’s life would suffice to express them. Some particular “word” has to be known before the lock of the safe will act, and some “cipher” is necessary before that cryptogram can be read.
He who had just reperused the document was but a simple “captain of the woods.” ”

“ The subject which we are about to study is the analysis and solution of cipher, though not including code, which is a very special form of cipher demanding something more than elementary knowledge; nor shall we enter at all into the subject of invisible inks, certainly a most important aspect of secret writing, but belonging to the province of chemistry rather than to that of cryptanalysis. Cipher machines, also, are not within our present scope. ”

“ This division into groups of a constant number of letters eliminates word forms and, in the mind of the non-expert, increases [96] the difficulty of solving the cipher. But the increase in difficulty is more apparent than real; particularly, as a cipher examiner habitually finds himself dealing with ciphers without word forms, and the occurrence of a cipher with word forms usually means that he has an easy one to handle. ”

“ The Playfair cipher may be recognized by the following points: (a) It is a substitution cipher, (b) it always contains an even number of letters, (c) when the cipher is divided into groups of two letters each, no group consists of the repetition of the same letter as SS or BB, (d) there will be recurrence of pairs throughout the message, following in a general way, the frequency table of digraphs of pairs, (e) in short messages there may be recurrence of cipher groups representing words or even phrases, and these will always be found in long messages. ”

“ If the whole of a telegraphic or radio message is in cipher, it is highly probable that the preamble, “place from,” etc., are in an operators’ cipher and are distinct from the body of the message. As these operators’ ciphers are necessarily simple, an attempt should always be made to discover, by methods of analysis to be set forth later, the exact extent of the operator’s cipher and then to decipher the parts of the messages enciphered with it.
In military messages, we almost invariably find the language of the text to be that of the nation to which the military force belongs. ”

“ At all events, some simple yet secure cipher, easily acquired and easily read, should be introduced, by which means messages might to all intents and purposes be “sealed” to any person except the recipient. We have reason to believe that Professor Wheatstone has invented a cipher of this description, which will speedily be made public. “One-eighth of the despatches between New Orleans and New York,” says Mr. Jones in his “Historical Sketch of the Electric Telegraph,” “are in cipher. ”

“ When I looked back over the letters translated from the cipher thus depleted, I found to my inexpressible joy that the sequence and sense were almost complete. The translation read as follows:
"To read the history of the Trust use cipher of Fr. Bacon. The senses and the figures are less worthy than the Trinity B. de E."
One step more and my work was done. I set the discarded numbers in sequence on another sheet of paper, and found to my intense satisfaction they formed an inner record readable by the same key. ”

“ The cipher of the amateur, or of the non-expert who makes one up for some special purpose, is almost sure to fall into one of the classes whose solution is an easy matter. The human mind works along the same lines, in spite of an attempt at originality on the part of the individual, and this is particularly true of cipher work because there are so few sources of information available. ”

“ Even book cipher, notably secure, however unwieldy in use, has been decrypted because of the encipherer’s very human tendency to use a substitute more than once rather than search for a new one among the hundreds at his disposal.
In book cipher, any agreed book, or other written or printed document, will serve as a key-volume, so long as it is one that is sure to be at hand when wanted. Words, or letters, can then be represented by a series of numbers usually indicating: page, (column) , line, serial position. One letter or one word may thus have a substitute such as 20-1-4-32. ”

“ A factor of particularly grave importance in the selection of a cipher to fit a given purpose is the probable amount of enciphered material which is going to fall into the possession of unauthorized persons. A criminal, who has had to send but one brief cryptogram in a lifetime, might reasonably expect that it will remain forever unread, no matter how weak the cipher. A commercial firm, transmitting thousands of words over the air, is more vulnerable ”

“ Concealment cipher has, of course, the unique virtue of being able to convey messages under circumstances which make it seem that no communication has passed, and we have hardly touched upon the fact that the short message, prior to its concealment, may have been a well-enciphered one. But we rather suspect that, for the end desired, invisible inks are more convenient and practical. ”

“ Analysis of the cipher with transliteration into modern square Hebrew characters. A translation into English. N.B. The cipher reads from right to left.
The Professor's Analysis.
He handed me the two papers, of which one gave the actual words of the cryptogram, and the other a suggested reconstruction, with omitted words supplied. The first read:
"Woe city lies robbery prey noise whip rattling wheel horse chariot day darkness gloominess cloud darkness morning mountain people strong fire them flame." ”

“ In some of the periodic ciphers, the basic cipher alphabet is a “checkerboard” of the kind we saw in Chapter XI, the substitutes being two-digit numbers which will point out the columns and rows of their originals. This primary alphabet, however, seldom appears unchanged in the cryptograms, as “position 1” often does when a slide is used, or as the A-alphabet often does in the Vigenère cipher. Instead, we find a series of secondary cipher alphabets all of which have been derived from the primary one according to a mathematical process. ”

“ I realized almost at once that I was dealing with a cipher or cryptogram; and I reflected that it was likely to be of a pretty simple kind, considering its early date. So I copied the letters with the most anxious care. Another little point, I may tell you, turned up in the process which confirmed my belief in the cipher. After copying the letters on Job's robe I counted them, to make sure that I had them right. There were thirty-eight ”

“ When this cipher is used for puzzle purposes, as we find it in our newspapers and popular magazines, the substitutes (which are invariably letters of the alphabet) may be chosen at random, and the cryptograms must follow certain arbitrary rulings which are designed to make them “fair”: Word-divisions and punctuation must follow religiously those of the original text; a certain minimum of length must be provided; no letter may act as its own substitute; foreign words are not permissible ”