Читать книгу Secret and Urgent - The Story of Codes and Ciphers - Анон - Страница 10

He was instantly and violently attacked. In the first place he was attacked by research chemists, who pointed out that the vellum surface on which the Roger Bacon manuscript had been written was rough, and the ink used in writing the famous document exceedingly thick, almost the consistency of printer’s ink. Examination of very old printed records on vellum under the microscope showed the ink breaking up into spots and shadings in almost the same fashion as in the Roger Bacon document.

There was an answer to this objection; no other manuscripts written with the same type of ink had ever been found. The oldest printed documents, with comparable ink, were nowhere near as aged as the Roger Bacon manuscript, the cracking of the ink had not gone so far in them, and the method of application had not been the same in the beginning. Moreover the manuscript was obviously a cipher of some sort, and Dr. Newbold had identified only twenty-two characters; an entirely accidental arrangement of dots and shadings would almost certainly have produced more. The criticism was important only in introducing one more element of doubt to those presently brought forward by cryptographers.

The first of these cryptographic doubts was concerned with the two steps of Dr. Newbold’s decipherment which dealt with pairs of letters. To understand the objection it is necessary to reverse the process he used and encipher a short text by the biliteral method. A frame is constructed on some such lines as these:

The clear is now enciphered by substituting for each letter the pair of letters which describe its position in the frame. N = HC or CH, for example. If the words “Come here” are thus enciphered the result is:

FC–HD–HB–FE–GC–FE–IB–FE

This is the first step in the double biliteral cipher which Dr. Newbold had described Roger Bacon as taking; and the next step is to substitute for these pairs of letters in the message, other pairs of letters, according to a definite system, which result in the completely enciphered message consisting of interlocking paired letters on the system (mentioned above) CO, OM, ME, EH, HE, ER, RE.

But it can readily be seen that the first pairs of letters enciphered by means of this frame do not interlock; and if the first set will not interlock, neither will the second, nor can they be made to interlock by any process whatever. The Newbold decipherment depends wholly on this interlocking feature, for unless the pairs of letters interlock at the second stage of this encipherment, they cannot be reduced from pairs of complementary letters to single letters for insertion into the shorthand; for shorthand, it will be recalled, was the last step of the encipherment, the first of the decipherment.

Dr. Newbold had an answer here also. Roger Bacon, he said, had not necessarily enciphered his text by the use of such a frame. In fact it was altogether likely that he had done nothing of the sort. What process he had used it was now impossible to say; the decipherment by interlocking pairs of letters was simply a method of approximating the result reached by Bacon along another route. But a second element of doubt had now been introduced.

The anagramming process which came at the end of the decipherment was attacked most heavily of all. The first quality of any good cipher is that it must convey its message with absolute certainty; that it should have two possible interpretations is absolutely inadmissible. Conversely, the first requirement of a decipherment is that it must be the only possible answer. But this is precisely what the Newbold anagramming process was not; for given the random assortment of letters that resulted from the last step but one of Dr. Newbold’s process, it was perfectly possible to construct another text than the one he found. Indeed, the English astronomer Proctor demonstrated that with a text as long as the one resulting from the early stages of the Newbold decipherment, the chances were several millions to one that it could be anagrammed into any clear the decipherer consciously or unconsciously desired to find, thanks to the frequencies of letters in the language. Indeed, one of the United States Army cryptographers, by applying exactly the same anagramming process to the dedication of Shakespeare’s First Folio, has been able to read into it a startling prophecy, beginning “Heil Hitler! Roosevelt is C.I.O. He is using the F.B.I. to turn the country Red.”

The objection was fatal, and the thing that rendered it fatal was the drawings on which the decipherment was based. Not one of the biological pictures was a clear and certain representation of the life-processes described in Dr. Newbold’s decipherment of the accompanying text. They were cabalistic, symbolical, vague and capable of various interpretations. In one notable instance Dr. Newbold’s interpretation was almost certainly wrong. He had deciphered the caption under a drawing of a great spirally-toothed circle to mean that it was a representation of the great spiral nebula in Andromeda. Now the spiral nebula in Andromeda lies edge on to the earthly observer; even quite a powerful telescope shows it as an uncertain egg-shaped mass. It was only years after its examination with the best telescopes, and then with the aid of elaborate electrical apparatus, that its spiral character was detected, and no one claimed that Bacon had invented electrical measuring devices or anything that would approximate their results.

Finally, on the general process it was extremely unlikely that Bacon would have used a cipher with so many steps; there is no instance of even a two-step cipher being used for many centuries after his time, and a one-step simple substitution cipher would have adequately baffled any man in his century.

Nor did the decipherment stand up very well in the long run. Neither Dr. Newbold nor anyone else using his system was able to get a sensible reading from the pages of the mysterious manuscript which had no drawings, and to this day it lies there waiting for a cryptographer who can eliminate the element of doubt.