CRYPTOGRAPHY (Gk. 7,:rmitos, secret 7pr'zoetr, graphein, to write). The art of writing messages and documents in cipher, in tended to be read only by those possessing the key. The use of secret methods of correspondence on important matters of state is of considerahle antiquity. Plutarch and Gellius tell of a method employed by Spartan epho•s in communicating with their generals abroad, which has received the name of scytale. from the staff used in decipher ing it. A narrow strip of parchment was first wound spirally upon the staff, its edges just meet ing. and the message was then written along the line of jointure. When it was unwound. the broken letters could afterwards be read only by rolling the parchment upon a duplicate stall' in possession of the general to whom it was sent. This is but one of a large number of mechanical devices for reading secret dispatches, such as papers pierced with holes, to be laid over the document, revealing only such words or letters as compose the secret message.
Cryptography, in its stricter sense of the use of a cipher alphabet formed either by changing the value of the different letters, or by substituting for them groups of letters, numbers, or arbitrary symbols, if not of Semitic origin, was at least already, known to, and used by, the sacred writers, in its simplest form of using the alphabet in its inverted order. By the Jews this form is known try the name of Athos, a word formed from A. the first letter of the Ilebrew alphabet; T, the last letter; 11, the second; and 5, the last but ono. An instance of its use occurs in denmiali xiv., where the prophet, wishing to veil his meaning from all hut the initiated, writes Shell:tell instead of Babel, using the second and twelfth letters from the end of the alphabet, instead of (non the beginning. Julius Cwsar's 'quarto elementoriun littera,' in which 1) takes the place of A. and E f B. is only a variant of this simplest form of cipher, and Suetonius states that a like method was employed by Augustus. In mediteval and modern times, many scholars have turned their attention to cryptography, among them John Trithemills, Abbot of Sponheini, in his Poliyra phi(' ( 1.500) ; Anastasius Kircher, and his pupil, Kaspar Schott, whose work, Dc Mogia Unirer•uli (Wiirzburg, 167G) , contains a crypto graphic table that lies at the foundation of the modern cipher telegraph systmns. It consists simply of the alphabet repeated twenty-four times in horizontal rows, each successive row dropping off one or more letters from the begin ning, and adding it at the end. Thus, in the second row, B stands under A, C under B, etc. In the third C represents A, in the fourth I) = A, et e. Thus correspondents have a choice of twenty
four alphabets, it being necessary only to agree between themselves upon the first or key letter. For diplomatic purposes, this form is much too shople, since any one could decipher dispatches made in this way, by the simple mechanical task of making at most twenty-four versions. Accord higly, various methods of complicating the cipher have been tried, one simple and effeetive way be ing that which is known in France as the method of Saint-Cyr. It consists in using alternately two or more of these twenty-four alphabets, the order in which they are to be used being determined by a key-word previously agreed upon. Thus, if the key-word is Army, four alphabets are to be used, namely those in the rows beginning respec tively with A, R, N. and Y. Various other elabo rations have been sometimes employed, such as arbitrarily changing the sequence of the letters of the alphabet, inserting at regular intervals letters or symbols that have no meaning, "nulls and insignificants," Bacon called them, or using groups of letters to represent separate letters. Of the last-named variety is the famous biliteral cipher of Bacon himself, consisting of various combinations of A and 11, arranged in groups of five. Thus, aabab, a babe, babba = Used in this way, such a cipher would be but little more difficult to detect than any ordinary set of single symbols. But Bacon went a step further; for the as and the b's of his groups he substituted two fonts of type, differing so slightly as to present little distinction to the un trained eye. These. called respectively the a font and the b font, can be used for setting up any ordinary page of printed matter. when by the proper admixture of the two fonts, each suc cessive group of live letters on the page may be made to stand for a single letter in Haeon's hiliteral system. The fact that Bacon took a deep interest in cryptograms is probably the origin of Ignatius Donnelly's theory that the Shake spearean plays contain a cipher that if inter preted would prove that Bacon wrote them. And recently a still bolder attempt has been made by a certain Mrs. Gallup to apply the biliteral cipher to the early Shakespeare folios, in which, as is generally known, more than one variety of type was used. The general principle involved in flacon's method, that of representing the whole alphabet with groups and combinations of two symbols only, lies at the basis of many modern methods of signaling—the dot and dash of the Morse telegraphic code, the right and left waving of flags in military or naval signal ing, etc.