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CRYPTOGRAPHY (from Gr. Kpurrros, hidd...

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Originally appearing in Volume V07, Page 566 of the 1911 Encyclopedia Britannica.
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CRYPTOGRAPHY (from Gr. Kpurrros, hidden, and ypItOav, to write) , or See also:writing in See also:cipher, called also steganography (from Gr. ?reyav17, a covering), the See also:art of writing in such a way as to be incomprehensible except to those who possess the See also:key to the See also:system employed. The unravelling of the writing is called deciphering. Cryptography having become a distinct art, See also:Bacon (See also:Lord Verulam) classed it (under the name ciphers) as a See also:part of See also:grammar. See also:Secret modes of communication have been in use from the earliest times. The Lacedemonians had a method called the scytale, from the See also:staff (Q'KVrf)^f) employed in constructing and deciphering the See also:message. When the Spartan ephors wished to forward their orders to their commanders abroad, they See also:wound slantwise a narrow See also:strip of See also:parchment upon the o•KVT6Xr7 so that the edges met See also:close together, and the message was then added in such a way that the centre of the See also:line of writing was on the edges of the parchment. When unwound the See also:scroll consisted of broken letters; and in that See also:condition it was despatched to its destination, the See also:general to whose hands it came deciphering it by means of a UKVrhXr7 exactly corresponding to that used by the ephors. See also:Polybius has enumerated other methods of cryptography. The art was in use also amongst the See also:Romans. Upon the revival of letters methods of secret See also:correspondence were introduced into private business, See also:diplomacy, plots, &c.; and as the study of this art has always presented attractions to the ingenious, a curious See also:body of literature has been the result.

See also:

John See also:Trithemius (d. 1516), the See also:abbot of Spanheim, was the first important writer on cryptography. His Polygraphia, published in 1518, has passed through many See also:editions, and has supplied the basis upon which subsequent writers have worked. It was begun at the See also:desire of the See also:duke of See also:Bavaria; but Trithemius did not at first intend to publish it, on the ground that it would be injurious to public interests. A Steganographia published at See also:Lyons (? 1551) and later at See also:Frankfort (16o6), is also attributed to him. The next See also:treatises of importance were those of Giovanni Battista della Porta, the Neapolitan mathematician, who wrote De furtivis litterarum notis, 1563; and of Blaise de Vigenere, whose Traite See also:des chiffres appeared in See also:Paris, 1587. Bacon proposed an ingenious system of cryptography on the See also:plan of what is called the See also:double cipher; but while thus lending to the art the See also:influence of his See also:great name, he gave an intimation as to the general See also:opinion formed of it and as to the classes of men who used it. For when prosecuting the See also:earl of See also:Somerset in the See also:matter of the poisoning of See also:Overbury, he urged it as an See also:aggravation of the See also:crime that the earl and Overbury " had cyphers and jargons for the See also:king and See also:queen and all the great men,—things seldom used but either by princes and their ambassadors and ministers, or by such as See also:work or practise against or, at least, upon princes." Other eminent Englishmen were afterwards connected with the art. John See also:Wilkins, subsequently See also:bishop of See also:Chester, published in 1641 an See also:anonymous See also:treatise entitled See also:Mercury, or The Secret and See also:Swift Messenger,—a small but comprehensive work on the subject, and a timely See also:gift to the diplomatists and leaders of the See also:Civil See also:War. The deciphering of many of the royalist papers of that See also:period, such as the letters that See also:fell into the hands of the See also:parliament at the See also:battle of See also:Naseby, has by See also:Henry Stubbe been charged on the celebrated mathematician Dr John See also:Wallis (See also:Aiken. Oxon. iii.

1072), whose connexion with the subject of cipher-writing is referred to by himself in the See also:

Oxford edition of his mathematical See also:works, 1689, p. 659; as also by John Davys. Dr Wallis elsewhere states that this art, formerly scarcely known to any but the secretaries of princes, &c., had grown very See also:common and See also:familiar during the civil commotions, " so that now there is scarce a See also:person of quality but is more or-less acquainted with it, and doth, as there is occasion, make use of it." Subsequentwriters on the subject are John See also:Falconer (Cryptomenysis pate-facia), 1685; John Davys (An See also:Essay on the Art of Decypheringt in which is inserted a Discourse of Dr Wallis), 1737; See also:Philip Thicknesse (A Treatise on the Art of Decyphering and of Writing in Cypher), 1772; See also:William See also:Blair (the writer of the comprehensive See also:article " Cipher " in See also:Rees's Cydopaedia), 1819; and G. von See also:Marten (Cours diplomatique), 18or (a See also:fourth edition of which appeared in 1851). Perhaps the best See also:modern work on this subject is the Kryptographik of J. L. Klaiber (See also:Tubingen, 1809), who was See also:drawn into the investigation by inclination and See also:official circumstances. In this work the different methods of cryptography are classified. Amongst others of lesser merit who have treated of this art may be named Gustavus Selenus (i.e. See also:Augustus, duke of See also:Brunswick), 1624; Cospi, translated by Niceron in 1641; the See also:marquis of Worchester, 1659; See also:Kircher, 1663; Schott, ,665; See also:Ludwig Heinrich See also:Hiller, 1682; Comiers; 169o; See also:Baring, 1737; See also:Conrad, 1739, &c. See also a See also:paper on Elizabethan Cipher-books by A. J. See also:Butler in the See also:Bibliographical Society's Transactions, See also:London, 1901.

Schemes of cryptography are endless in their variety. Bacon See also:

lays down the following as the " virtues " to be looked for in them:—" that they be not laborious to write and read; that they be impossible to decipher; and, in some cases, that they be without suspicion." These principles are more or less disregarded by all the modes that have been advanced, including that of Bacon himself, which has been unduly extolled by. his admirers as" one of the most ingenious methods of writing in cypher, and the most difficult to be decyphered, of any yet contrived " (Thicknesse, p. 13). The simplest and commonest of all the ciphers is that in which the writer selects in See also:place of the proper letters certain other letters in See also:regular advance. This method of transposition was used by See also:Julius See also:Caesar. He, " per quartam elementorum literam," wrote d for a, e for b, and so on. There are instances of this arrangement in the Jewish rabbis, and even in the sacred writers. An See also:illustration of it occurs in See also:Jeremiah (See also:xxv. 26), where the See also:prophet, to conceal the meaning of his prediction from all but the initiated, writes Sheshak instead of See also:Babel (See also:Babylon), the place meant; i.e. in place of using the second, and twelfth letters of the See also:Hebrew See also:alphabet (b, b, l) from the beginning, he wrote the second and twelfth (sh, sh, k) from the end. To this See also:kind of cipher-writing See also:Buxtorf gives the name Athbash (from a the first See also:letter of the Hebrew alphabet, and th the last; b the second from the beginning, and h the second from the end). Another Jewish cabalism of like nature was called Albam; of which an example is in See also:Isaiah vii. 6, where Tabeal is written for Remaliah.

In its See also:

adaptation to See also:English this method of transposition, of which there are many modifications, is comparatively easy to decipher. A rough key may be derived from an examination of the respective quantities of letters in a type-founder's See also:bill, or a printer's " See also:case." The decipherer's first business is to classify the letters of the secret message in the See also:order of their frequency. The letter that occurs oftenest is e; and the next in order of frequency is t. The following See also:groups come after these, separated from each other by degrees of decreasing recurrence:—a, o, n, i; r, s, h;, d, l; c, w, u, m; f, y, g, p, b; v, k; x, q, j, z. All the single letters must be a, I or O. Letters occurring together are ee, oo, if, ll, ss, &c. The commonest words of two letters are (roughly arranged in the order of their frequency) of, to, in, it, is, be, he, by, or, as, at, an, so, &c. The commonest words of three letters are the and and (in great excess), for, are, but, all, not, &c.; and of four letters—that, with, from, have, this, they, &c. Familiarity with the See also:composition of the See also:language will suggest numerous other points that are of value to the decipherer. He may obtain other hints from See also:Poe's See also:tale called The See also:Gold See also:Bug. As to messages in the See also:continental See also:languages constructed upon this system of trans-position, rules for deciphering may be derived from Breithaupt's Ars decifratoria (1737), and other treatises. Bacon remarks that though ciphers were commonly in letters and alphabets yet they might be in words.

Upon this basis codes have been constructed, classified words taken from dictionaries being made to represent See also:

complete ideas In See also:recent years such codes have been adapted by merchants and others to communications by See also:telegraph, and have served the purpose not only of keeping business affairs private, but also of reducing the excessive cost of telegraphic messages to distant markets. Obviously this class of ciphers presents greater difficulties to the skill of the decipherer. Figures and other characters have been also used as letters; and with them ranges of numerals have been combined as the representatives of syllables, parts of words, words themselves, and complete phrases. Under this See also:head must be placed the despatches of Giovanni See also:Michael, the Venetian See also:ambassador to See also:England in the reign of Queen See also:Mary, documents which have only of See also:late years been deciphered. Many of the private letters and papers from the See also:pen of See also:Charles I. and his queen, who were adepts in the use of ciphers, are of the same description. One of that monarch's letters, a document of considerable See also:interest, consisting entirely of numerals purposely complicated, was in 1858 deciphered by See also:Professor See also:Wheatstone, the inventor of the ingenious crypto - See also:machine, and printed by the Philobiblon Society. Other letters of the like See also:character have been published in the First See also:Report of the Royal See also:Commission on See also:Historical See also:Manuscripts (1870). In the second and subsequent reports of the same commission several keys to ciphers have been catalogued, which seem to refer themselves to the methods of cryptography under See also:notice. In this connexion also should be mentioned the " characters," which the diarist See also:Pepys See also:drew up when clerk to See also:Sir See also:George See also:Downing and secretary to the earl of See also:Sandwich and to the See also:admiralty, and which are frequently mentioned in his See also:journal. Pepys describes one of them as " a great large character," over which he spent much See also:time, but which was at length finished, 25th See also:April 166o; " it being," says he, " very handsomely done and a very See also:good one in itself, but that not truly alphabetical." Shorthand marks and other arbitrary characters have also been largely imported into cryptographic systems to represent both letters and words, but more commonly the latter. This plan is said to have been first put into use by the old See also:Roman poet See also:Ennius. It formed the basis of the method of See also:Cicero's freedman, Tiro, who seems to have systematized the labours of his predecessors.

A large quantity of these characters have been engraved in See also:

Gruter's Inscriptiones. The correspondence of See also:Charlemagne was in part made up of marks of this nature. In Rees's Cyclopaedia specimens were engraved of the cipher used by See also:Cardinal See also:Wolsey at the See also:court of See also:Vienna in 1524, of that used by Sir See also:Thomas See also:Smith at Paris in 1563, and of that of Sir See also:Edward See also:Stafford in 1586; in all of which arbitrary marks are introduced. The first English system of shorthand—Bright's Characterie, 1588—almost belongs to the same See also:category of ciphers. A favourite system of Charles I., used by him during the See also:year 1646, was one made up of an alphabet of twenty-four letters, which were represented by four See also:simple strokes varied in length, slope and position. This alphabet is engraved in See also:Clive's Linear System of Shorthand (183o), having been found amongst the royal manuscripts in the See also:British Museum. An interest attaches to this cipher from the fact that it was employed in the well-known letter addressed by the king to the earl of Glamorgan, in which the former made concessions to the Roman Catholics of See also:Ireland. Complications have been introduced into ciphers by the employment of " dummy " letters,—" nulls and insignificants," as Bacon terms them. Other devices have been introduced to perplex the decipherer, such as spelling words backwards, making false divisions between words, &c. The greatest See also:security against the decipherer has been found in the use of elaborate tables of letters, arranged in the See also:form of the multiplication table, the message being constructed by the aid of preconcerted key-words. Details of the working of these ciphers may be found in the treatises named in this article. The deciphering of them is one of the most difficult of tasks.

A method of this kind is explained in the Latin and English lives of Dr John Barwick, whose correspondence with See also:

Hyde, afterwards earl of See also:Clarendon, was carried on in cryptography. In a letter dated loth See also:February 1659/6o, Hyde, alluding to the skill of his See also:political opponents in deciphering, says that " nobody needs to fear them, if theywrite carefully in good cyphers." In his next he allays Es correspondent's apprehensiveness as to the deciphering of their letters. " I confess to you, as I am sure no copy could be gotten of any of my cyphers from hence, so I did not think it probable that they could be got on your See also:side the See also:water. But I was as confident, till you tell me you believe it, that the See also:devil himself cannot decypher a letter that is well written, or find that Roo stands for Sir H. See also:Vane. I have heard of many of the pretenders to that skill, and have spoken with some of them, but have found them all to be mountebanks; nor did I ever hear that more of the King's letters that were found at Naseby, than those which they found decyphered, or found the cyphers in which they were See also:writ, were decyphered. And I very well remember that in the See also:volume they published there was much See also:left in cypher which could not be understood, and which I believe they would have explained if it had been in their See also:power." An excellent modification of the key-word principle was constructed by See also:Admiral Sir See also:Francis See also:Beaufort. Ciphers have been constructed on the principle of altering the places of the letters without changing their See also:powers. The message is first written See also:Chinese-See also:wise, upward and downward, and the letters are then combined in given rows from left to right. In the celebrated cipher used by the earl of See also:Argyll when plotting against See also:James II., he altered the positions of the words. Sentences of an indifferent nature were constructed, but the real meaning of the message was to be gathered from words, placed at certain intervals. This method, which is connected with the name of See also:Cardan, is sometimes called the trellis or card-See also:board cipher.

The See also:

wheel-cipher, which is an See also:Italian invention, the See also:string-cipher, the circle-cipher and many others are fully explained, with the necessary diagrams, in the authorities named above—more particularly by Kluber in his Kryptographik. (J. E.

End of Article: CRYPTOGRAPHY (from Gr. Kpurrros, hidden, and ypItOav, to write)

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