A Few Words on Secret Writing — July 1841 (historical reading)

A Few Words on Secret Writing — July 1841 Historical reading from James A. Harrison’s 1902 edition, volume XIV. This is a later collected text, not the original printing or a manuscript scan. Paragraph and verse-line boundaries are retained; typography is simplified. Cipher tables are rendered as text with tab-separated cells. This record covers the July essay; later supplements remain separate. A FEW WORDS ON SECRET WRITING.(1) [Graham's Magazine, July, 1841.] AS we can scarcely imagine a time when there did not exist a necessity, or at least a desire, of transmitting information from one individual to another in such manner as to elude general comprehension, so we may well suppose the practice of writing in cipher to be of great antiquity. De La Guilletière, therefore, who, in his “Lacedæmon Ancient and Modern,” maintains that the Spartans were the inventors of Cryptography, is obviously in error. He speaks of the scytala as being the origin of the art; but he should only have cited it as one of its earliest instances, so far as our records extend. The scytalæ were two wooden cylinders, precisely similar in all respects. The general of an army, in going upon any expedition, received from the ephori one of these cylinders, while the other remained in their possession. If either party had occasion to communicate with the other, a narrow strip of parchment was so wrapped around the scytala that the edges of the skin fitted accurately each to each. The writing was then inscribed longitudinally, and the epistle unrolled and dispatched. If, by mischance, the messenger was intercepted, the letter proved unintelligible to his captors. If he reached his destination safely, however, the party addressed had only to involve the second cylinder in the strip to decipher the inscription. The transmission to our own times of this obvious mode of cryptography is due, probably, to the historical uses of the scytala rather than to anything else. Similar means of secret intercommunication must have existed almost contemporaneously with the invention of letters. It may be as well to remark, in passing, that in none of the treatises on the subject of this paper which have fallen under our cognisance have we observed any suggestion of a method — other than those which apply alike to all ciphers — for the solution of the cipher by scytala. We read of instances, indeed, in which the intercepted parchments were deciphered; but we are not informed that this was ever done except accidentally. Yet a solution might be obtained with absolute certainty in this manner. The strip of skin being intercepted, let there be prepared a cone of great length comparatively — say six feet long — and whose circumference at base shall at least equal the length of the strip. Let this latter be rolled upon the cone near the base, edge to edge, as above described; then, still keeping edge to edge, and maintaining the parchment close upon the cone, let it be gradually slipped towards the apex. In this process, some of those words, syllables, or letters, whose connection is intended, will be sure to come together at that point of the cone where its diameter equals that of the scytala upon which the cipher was written. And as, in passing up the cone to its apex, all possible diameters are passed over, there is no chance of a failure. The circumference of the scytala being thus ascertained, a similar one can be made, and the cipher applied to it. Few persons can be made to believe that it is not quite an easy thing to invent a method of secret writing which shall baffle investigation. Yet it may be roundly asserted that human ingenuity cannot concoct a cipher which human ingenuity cannot resolve. In the facility with which such writing is deciphered, however, there exist very remarkable differences in different intellects. Often, in the case of two individuals of acknowledged equality as regards ordinary mental efforts, it will be found that, while one cannot unriddle th