The Complete Works of Edgar Allan Poe - Edgar Allan Poe [644]
( might be employed for a
. " " " b
" " " c
" " " d
) " " " e &c.
A letter composed of such characters would have an intricate appearance unquestionably. If, still, however, it did not give full satisfaction, the idea of a perpetually shifting alphabet might be conceived, and thus effected. Let two circular pieces of pasteboard be prepared, one about half an inch in diameter less than the other. Let the centre of the smaller be placed upon the centre of the larger, and secured for a moment from slipping; while radii are drawn from the common centre to the circumference of the smaller circle, and thus extended to the circumference of the greater. Let there be twenty-six of these radii, forming on each pasteboard twenty-six spaces. In each of these spaces on the under circle write one of the letters of the alphabet, so that the whole alphabet be written-- if at random so much the better. Do the same with the upper circle. Now run a pin through the common centre, and let the upper circle revolve, while the under one is held fast. Now stop the revolution of the upper circle, and, while both lie still, write the epistle required; using for a that letter in the smaller circle which tallies with a in the larger, for b that letter in the smaller circle which tallies with b in the larger &c. &c. In order that an epistle thus written may be read by the person for whom it is intended, it is only necessary that he should have in his possession circles constructed as those just described, and that he should know any two of the characters (one in the under and one in the upper circle) which were In juxta-position when his correspondent wrote the cipher. Upon this latter point he is informed by looking at the two initial letters of the document, which serve as a key. Thus, if he sees a m at the beginning, he concludes that, by turning his circles so as to put these characters in conjunction, he will arrive at the alphabet employed.
At a cursory glance, these various modes of constructing a cipher seem to have about them an air of inscrutable secrecy. It appears almost an impossibility to unriddle what has been put together by so complex a method. And to some persons the difficulty might be great; but to others--to those skilled in deciphering--such enigmas are very simple indeed. The reader should bear in mind that the basis of the whole art of solution, as far as regards these matters, is found in the general principles of the formation of language itself, and thus is altogether independent of the particular laws which govern any cipher, or the construction of its key. The difficulty of reading a cryptographical puzzle is by no means always in accordance with the labor or ingenuity with which it has been constructed. The sole use of the key, indeed, is for those au fait to the cipher; in its perusal by a third party, no reference is had to it at all. The lock of the secret is picked. In the different methods of cryptography specified above, it will be observed that there is a gradually increasing complexity. But this complexity is only in shadow. It has no substance whatever. It appertains merely to the formation, and has no bearing upon the solution, of the cipher. The last mode mentioned is not in the least degree more difficult to be deciphered than the first--whatever may be the difficulty of either.
In the discussion of an analogous subject, in one of the weekly papers of this city, about eighteen months ago, the writer of this article had occasion to speak of the application of a rigorous method in all forms of thought--of its advantages--of the extension of its use even to what is considered the operation of pure fancy--and thus, subsequently, of the solution of cipher. He even ventured to assert that no cipher, of the character above specified,