Ciphers of the Revolutionary Period (1917 article)



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Ciphers of the Revolutionary Period

During the Revolutionary period cipher was employed extensively not only in public correspondence where secrecy was especially important but in the private correspondence of public men as well. It is true that most of the letters written in cipher that have come down to us are accompanied by some form of translation, oftenest an interlinear decipherment by the recipient; yet the quantity of writing that has remained undeciphered is in the aggregate considerable. There are, for instance, numerous undeciphered passages in the published writings of Jefferson, Madison, and Monroe, as well as in letters of theirs that have not been printed.

Of ciphers used in the period under consideration five different types have been encountered: first, a mere transposition of the alphabet; second, a dictionary or book cipher; third, a sentence or longer passage used as a key, the letters being numbered in the order in which they occur; fourth, a columnar table of alphabets built upon a key-word; and, fifth, a collection of words, syllables, and letters more or less arbitrarily arranged and numbered. The transposition of the alphabet, a mere substitution of one letter for another, was not apparently much used.

The book cipher was employed rather extensively, particularly in the earlier part of the period. In its simplest form its use required only the possession, by each of the correspondents, of the same edition of a dictionary. A notable instance of a dictionary cipher is found in the correspondence of Arthur, Richard Henry, and William Lee in the years 1777-1779. As used by them an arabic numeral designates the page, an a or a & the column, and a roman numeral the line. The book was probably Entick's New Spelling Dictionary, edition of 1777. As no copy of the edition used could be found the process of solution by the present writer consisted in, first, the identification of certain ciphers from the context, next, locating these words in the edition of 1782 (the nearest to 1777 obtainable), and then, by a process of approximation, determining other words.

Of the third sort of cipher mentioned the principal example come upon is that used by C. W. F. Dumas. It is evidently this code that is found in the Franklin Papers in the American Philosophical Society. The key is a long passage in French running to 682 letters, numbered consecutively. In such a cipher each letter has several numbers corresponding to it, which may be used indifferently.

The fourth form of cipher is made by taking a key-word and constructing columns of alphabets beginning with the letters of the word in the order of their occurrence and numbered from 1 to 26 or 27 (when 27 letters are used the character & follows Z). In writing in this cipher the letters are sought in the columns successively and the corresponding numbers are used. This form of cipher seems to have been introduced by James Lovell when he was a member of the Committee of Foreign Affairs, and was used by him in letters to John Adams, Mrs. Abigail Adams, and others. Livingston, when he became secretary for foreign affairs, used the same cipher in his first correspondence with Adams, and Jefferson used such a cipher in some earlier correspondence with William Short.

The most noteworthy series of letters in a cipher of this sort were written by Madison to Edmund Randolph in the summer and autumn of 1782. These letters have never hitherto been deciphered. In fact Randolph himself was never able to decipher them, owing partly, no doubt, to certain errors which Madison made in writing the cipher. Although these errors occasioned some difficulties the solution was accomplished through the successful guessing of the cipher for "commission", from which the alphabetical table was reconstructed.

It was the fifth type of cipher that came to be most generally employed. Such a cipher might consist of only a comparatively few numbers for persons, places, etc., or it might run to hundreds of items. While some ciphers of this type were sent abroad by Charles Thomson and Robert Morris in 1780 and 1781, not many examples of its use have been found prior to the autumn of 1781, when Robert R. Livingston became secretary for foreign affairs, after which individuals of the type were rapidly multiplied both for public and for private use. Livingston had some forms printed, having on one side of the sheet the numbers from 1 to 1700, on the other the alphabetical list of words, syllables, etc. These forms were a convenient basis on which correspondents could prepare their identical codes.

The earliest of these numerical codes which the writer has come upon is that used by the Virginia delegates to Congress in 1782 in their official correspondence with the governor. It is not on a printed form and runs to only 846 numbers. Madison and Randolph used this code to a considerable extent in their private correspondence also in that year. The several ciphers used by Jefferson, Madison, and Monroe from 1783 on require some explication. In January and February, 1783, Jefferson and Madison used a dictionary cipher. From April, 1783, to May, 1785, they used a numerical cipher, the key to which has not been found. Of some of these letters however there is a decipherment or translation (they are chiefly Madison's), and from these a code has been reconstructed by which the others have been deciphered. In the same period Monroe used in a few letters to Madison a numerical code of very limited extent, of which most of the ciphers used are interpreted in the texts of the letters. From May, 1785, to May, 1786, however, Madison and Monroe used a cipher for which no code has been found. In this case also it has been possible, by means of such decipherments as exist, to decipher (with the possible exception of occasional words) those letters for which there is no translation. The correspondence of Jefferson and Monroe from May, 1784, to March, 1785, offers some difficulties, but as the codes by which these letters were written are in existence a careful attention to the several explanations of the writers enables one to overcome these difficulties. In the spring of 1785 Jefferson prepared a new and more extensive code on the printed forms referred to above, which was thenceforward used in his correspondence with both Madison and Monroe and in theirs with him.

One incidental discovery, although somewhat afield from this particular investigation, deserves nevertheless to be recorded here. A short while ago a professor in a western university sent to the Department of Historical Research a body of letters from President Jackson to a diplomatic agent, of the year 1832, written in cipher, and asked whether some means might not be found of deciphering them. The department happened to have a cipher code, constructed on one of the printed forms heretofore referred to, found among the Monroe Papers in the New York Public Library, without date, and merely endorsed: "Mr. Monroe's cypher". It was found upon test that the Jackson letters were written in this code. It was further discovered that the same code was used by James A. Bayard when he was one of the commissioners for negotiating the Treaty of Ghent. It has since been learned that Monroe used this code in 1805 when he was minister to England. It was evidently therefore an official cipher.

 Edmund C. Burnett.