Secret and Urgent - The Story of Codes and Ciphers. Anon

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.

      CHAPTER III

      JARGON

      I

      LYSANDER of Sparta, commander of the city state’s armies in the north, sat in his house at Sestos. At the moment he was the most powerful man in the Greek world. A year had not gone by since he crushed forever the power of the Athenian Empire in the great sea-fight at Aegospotami, captured that proud imperial city, and sailed on to the Hellespont, where Greece met Persia, to put the world in order.

      Yet victory had brought problems as well as power. It was the nature of Greeks to be jealous; in overthrowing the parties that had held for Athens among the cities of the north his proceedings had necessarily been highhanded, and of late there had reached him from the home city nothing but an ominous silence. His position was the more difficult because precisely at this moment he had arrived at a parting of the ways of policy, a point where instruction as to the intent and position of the Spartan government was most needed.

      Pharnabazus, the Persian satrap who held the Asia Minor shores, had supported him and Sparta in their war with Athens. Outwardly, the Persian was friendly still; but Lysander had reason to believe that Persia looked with as much disfavor on a Greece united under Spartan hegemony as on a Greece united under Athens. The riots among the cities had seemed spontaneous, but there were not wanting signs that Persia had interfered.

      The question before Lysander was what course to take—what course the home government wished him to take. Action against Persia might precipitate a major Persian war for which Sparta was unprepared. Doing nothing might allow the anti-Spartan, pro-Athenian movement among the cities to gather such momentum it could not be halted. It was altogether possible that the home government was already planning on that great war with Persia which Lysander had discussed with them before leaving the city. If he went back to Sparta now, he might just miss the troops and ships coming north for the great adventure. This would be equal to desertion.

      As he meditated, a slave was brought in. The man said he was from Sparta, one of four, with messages from the government. Where the other three were he did not know; probably killed or taken somewhere along the route. He himself had been carried off to prison till those who held him were satisfied that he had no message beyond the innocuous one on his tablets, commanding Lysander to observe some religious festival.

      The general nodded, and asked the man for his belt, a narrow one of soft leather, written round with one of those meaningless jumbles of letters which the priests of certain mysteries prepare for travelers as invocations to the patron god of journeys, Hermes. The slave handed it over and was dismissed. When he had gone Lysander detached from his own belt the baton which always hung there, an article which those who did not know the Spartan system understood as merely the emblem of his office. The baton was pierced at the end farthest from the handle; through this hole Lysander inserted the end of the slave’s belt and wound the strip of leather spirally around the staff, close-packing it so that no wood was left bare between one circuit and the next.

      As he did so the dissociated letters, which had been merely gibberish while the belt lay in a straight line, were brought into a new relation to one another. Words and sentences leaped from loop to loop; Pharnabazus had played false to the general and to Sparta. Lysander’s friend Thorax had been murdered; his messages to the home city evidently had been intercepted, and there was a bribery complaint against him before the government. Since