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A curious and half-forgotten chapter in the life of Edgar Allan Poe is the one which deals with his researches in the field of \"Secret Writing,\" and his extraordinary ability in inventing and analysing ciphers.
In \"The Gold Bug\" he gave a singularly clear description of the method of translating a cipher message. At first sight the cipher in the story, with its mingling of letters, figures and symbols, appears bafflingly formidable; but after Poe has started the scent by pointing out that which should have been at once perfectly obvious, one is ready and eager to carry out the reading of the message for himself. But Poe was not merely able to invent and analyse systems of secret writing; he stood ready to decipher those which others would submit to him. He even went so far as to assert, in a Philadelphia weekly paper on which he was employed, that no cipher could be sent to him that he would not be able to solve. This challenge excited a lively interest among the readers of the paper, and letters were sent to him from all parts of the country. In many cases the writers were not strictly scrupulous in observing the conditions of the challenge. Foreign languages were used. Words and sentences were run together without interval. Several alphabets were employed in the same cipher. And yet out of, perhaps, one hundred ciphers received there was but one which Poe did not succeed immediately in solving, and that one proved to be an imposition, a jargon of random characters having no meaning whatever.
But by the public at large, Poe\'s feat was looked upon in the light of a gigantic humbug. Some averred that the mysterious characters were inserted for the purpose of giving an odd look and thereby advertise the paper. Others fancied that Poe not only solved the ciphers, but put them together for solution. In fact, very few, with the exception of those who had written the ciphers, really believed in the authenticity of the answers. And it was with the hope of dispelling these ideas of deception that Poe afterward wrote his papers on \"Secret Writing\" in the pages of Graham\'s Magazine. The first method of cryptography which Poe attacked and riddled was that of the scytalae of the Spartans, long considered impossible of solution. The scytalae were two wooden cylinders, precisely similar in every respect. The general of an army, starting on an expedition, received one of these cylinders, while the other remained in Sparta. To communicate, a narrow strip of parchment was so wrapped round the scytala that the edges of the skin fitted accurately each to each. The writing was then inscribed longitudinally, and the letter unrolled and dispatched. The general addressed had only to wrap the second cylinder in the strip to read the message. But as Poe pointed out, certain solution was easy enough. The strip intercepted, let there be prepared a cone of great length. Let the strip be rolled on the cone near the base, edge to edge; then still keeping edge to edge, and holding the parchment close to the cone, let it be slipped gradually toward the apex. In this way some of the letters whose connection is intended will come together at that point of the cone where its diameter equals that of the scytala on which the cipher was written; a similar cylinder can be obtained and the message read.
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