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

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СКАЧАТЬ 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 Lysander had not responded to their request for a reply to these charges (which he had never received) he would be presently judged guilty in absence and condemned.

      Within the night a fast galley bore Lysander of Sparta south, homeward through the Aegean; the first recorded use of cipher had saved a general and an empire, and set in motion the chain of circumstances that led unbroken to the triumph of West over East under Alexander the Great.

      II

      Suetonius, the Walter Winchell of ancient Rome, says that Julius Caesar kept his fingers on the political pulse of the home city by writing to his friends from Gaul in a cipher that was prepared by shifting each letter of the original clear four places down the alphabet. Habes opinionis meae testimonium, which he wrote to Cicero, would thus come out as MDEHV RSNQNRQNV PHDH XHVXNPRQNZP, allowing for the fact that the Roman alphabet lacked J, K, W and Y.

      Given that the science of solving ciphers had not yet been invented this simple system was enough to protect his correspondence from unauthorized eyes. However, we have the best of reasons for believing that Julius Caesar’s ciphers were neither used very long nor for the conveyance of very important information. Cicero was one of the people in the secret; and Cicero changed political sides, which meant that the great conqueror’s secret was a secret no longer. Moreover, a good many of Caesar’s letters in clear have been preserved. We know from them and from other sources that his usual method of secrecy was to say nothing in writing, but to appoint someone he trusted to carry a message orally.

      The only thing he really contributed to the history of secret writing was the use of his name. A cipher composed by displacing the letters of the alphabet two, three or more steps down the line is still known as a “Julius Caesar cipher” in spite of the fact that there is good evidence this type of communication was in use before he was born.

      III

      The ciphers of Sparta and Rome left no recognizable direct descendents. Roger Bacon’s, whatever one may think of the Newbold decipherment, was an isolated effort; and the interpretation of the records of the rocks took place at a time when cryptography was already highly developed. A certain Abbot Trithemius who wrote an early book on ciphers in Holland, says that Charlemagne used ciphers to communicate with his agents, but the tale stands on about the same basis as the confident medieval assertions that Virgil was a necromancer who could fly through the night on broomsticks. We know as a matter of historical fact that Charlemagne himself never learned to read or write any language till he reached maturity, and that most of the great officers of his court remained illiterate to the end. Any kind of writing would have been cipher enough in such an age.

      And if Charlemagne did use ciphers, it was another case of an isolated effort. The genuine sources of modern cryptography can be traced, vaguely and with some difficulty, to two widely separated medieval springs—clerkly authorship and thieves’ slang. The first may reasonably be looked upon as the beginning of ciphers and the latter of codes, but the two blend and divide like a slow stream passing many islands, and it is not until relatively modern times that they become sharply distinguished.

      It is a little difficult to realize today that during the Middle Ages literature was an extra-hazardous occupation. The Church exercised both a monopoly and a close censorship of it and used that censorship in a manner that seemed to contemporaries highly capricious. When a writer set down his thoughts, he knew for a certainty that sooner or later they would come to the attention of the Church authorities, but not what the result would be. Thus Roger Bacon’s writings were discovered to be highly heretical; he was put into prison. But the works of his pupil, Thomas Aquinas, were found not only good doctrine but extremely valuable, and he was canonized.

      Under the circumstances most medieval writers tried to conceal authorship by some device that would enable them to throw off the mask if the Church approved their work, but keep it up if she did not. One of these devices was that of anagramming the author’s name; Rabelais thus appeared as Messer Alcofribas, just as Monsieur Arouet junior (1.j.) was later to become famous under his anagram of Voltaire. The Newbold decipherment has at least the justification that anagramming was common practice at the time the Bacon manuscript was written.

      A more common device and one more important in the history of ciphers was that of suppressing the vowels in signatures and doubtful passages. There were two methods of doing this. One was to replace the vowels with dots on a regular system, I being represented by a single dot, A by two, E by three and 0 by four. (U, then written as V, was let alone.) Thus “Richard, Roi d’Angleterre” would become R.ch..rd, r..... d’..ngl...t...rr... The other system was to replace the five vowels, in their order, with B, F, K, P and X, making of “Archepiscopus Arnulfus” BRCHFPKSCPPXS BRNXLFXS. The second scheme violated one of the cardinal principles of cryptography by making it difficult to tell a letter of the clear from an enciphered letter; and both were so simple and so well known that they could hardly have deceived anyone, even in the Middle Ages. But as the objective seems to have been not so much complete deception as something to furnish a lawyer’s talking point in case the matter came before an ecclesiastical court, these simple devices seem to have served their purpose.

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