THE CODEBREAKERS

by DAVID KAHN

  Tousjours fortune te rira,

  Et, tant que guerre durera,

  Bellone † exaltera tes Chittres

  Parmy les tambours & les fiffres.

  31 There’s not a thing beneath the skies;

  That can be hidden from thine eyes;

  Those Lynceus eyes, which, I believe,

  Our most internal thoughts perceive.

  35 How marvelous thy skill, and bright,

  And how important thine art’s might!

  For with it provinces are gained,

  All princes’ secrets ascertained,

  And by it, with an effort small,

  40 Are towns and forts compelled to fall.

  57 Indeed, thy art’s beyond my ken

  And 1 shall never comprehend

  secret; but I now can tell

  60 That it hath served thee very well.

  Thou dost deserve it. Have no fears—

  Thy skill shall prosper thee for years.

  Too, Fortune will upon thee smile

  , And long as wars the land defile

  65 Bellona shall, in strife to come,

  Thy cipher praise, ‘midst fife and drum.

  Rossignol’s work gave him access to some of the greatest secrets of the state and the court, and consequently made him a figure of some prominence in the glittering court of Louis XIV. He appears in some of the major memoirs of that period. Tallement des Réaux tells some unflattering stories about him and calls him “a poor species of man” in his Historiettes. But the Duke of Saint-Simon, whose Mémoires are a monument of French literature, wrote that Rossignol was “the most skillful decipherer of Europe…. No cipher escaped him; there were many which he read right away. This gave him many intimacies with the king, and made him an important man.” Rossignol also became the first person to have his biography written solely because of his cryptologic abilities. Charles Perrault, who is better known as the formulator of the Mother Goose tales, included a two-page sketch of Rossignol’s life, complete with engraved portrait, in his “Illustrious Men Who Have Appeared in France During This Century,” in the company of such as Richelieu. Mazarin regarded his good will as important enough to write a letter of regret in 1658 for some injury done to Rossignol at Paris—and to follow it up two months later with a note to a court official pressing him to do justice to the cryptanalyst “for the insult and violence that has been done him.” A more particular sign of importance appears in the largesse that the king showered upon him: 14,000 écus in 1653, 150,000 livres in 1672, and an annuity, late in his life, of 12,000—to name just some of his payments.*

  All the power, wealth, flattery, and royal favor that came to Rossignol at court quite turned his small-town head. To pace the galleries of the Louvre with haughty dukes and princes of France, to wear rich lace-trimmed coats with enormous cuffs, and stockings of whitest silk, to play at that new game, billiards, with the king himself—and to have this publicized in an engraving—to run up bills at the wigmaker’s, to learn before the rest of the world did who had become the king’s new mistress, best of all, to return home to Albi exuding the aura of the court. “Monseigneur,” he gloated one day to Richelieu about his former neighbors, “they do not dare to approach me. They regard me as a favorite—me, who lives with them just as before. They are amazed at my civility.” Richelieu could only shrug his shoulders.

  Nevertheless, Rossignol’s abilities were undeniable. And they served France not only in cryptanalysis but in cryptography, where they wrought the most important technical improvement that nomenclators underwent in their 400-year reign.

  When Rossignol began his career, nomenclators listed both their plain and code elements in alphabetical order (or alphabetical and numerical order, if the code was numerical). Plain and code paralleled one another. This relatively simple arrangement had existed since nomenclators emerged during the early Renaissance. The only deviation occurred in occasional small nomenclators when short lists of names were written down haphazardly; the code elements, however, always ascended in alphabetical order. Rossignol must have soon observed in his cryptanalyses that parallelism of plain and code assisted him in recovering plaintext. If, for example, he ascertained in an English dispatch that 137 stood fox for and 168 for in, he would know that 21 could not represent to because codenumbers for words beginning with t would have to stand higher than those for words beginning with i. Moreover, he would know that the codenumber for from, which comes alphabetically between for and in, would have to fall between their codenumbers 137 and 168, and he could search accordingly.

  From here, it was a simple step to depriving other cryptanalysts of such clues by destroying the parallel arrangement. This he did, mixing the code elements relative to the plain. Two lists were now required, one in which the plain elements were in alphabetical order and the code elements randomized, and one to facilitate decoding in which the code elements stood in alphabetical or numerical order while their plain equivalents were disarranged. These two lists soon came to be called “tables à déchiffrer” and “tables à déchiffrer,” and the mixed type of nomenclator became a “two-part” nomenclator to contrast it with the older “one-part” type. The two-part nomenclator has been compared to a bilingual dictionary. In the first half, the native words are listed alphabetically and the foreign appear in mixed order; in the second half, the foreign words progress alphabetically and the native words are jumbled.

  This innovation apparently began to go into service about the middle of Rossignol’s stewardship. Circumstances probably deserve most of the credit for his getting the idea first. At that time, other countries employed different people for making nomenclators and for breaking them. The cryptanalysts were called in only when needed; clerks compiled the nomenclators. France alone was rich and active enough to need and support a full-time cryptanalyst, who could also apply his knowledge to improving France’s secret communications.

  The two-part construction spread rapidly to other countries. At the same time, nomenclators continued to grow. The greater the size the greater the security, for it meant just that many more elements that the cryptanalyst had to recover. By the 1700s some nomenclators ran to 2,000 or 3,000 elements. But these were very expensive to compile in two-part form, and so, for reasons of economy and to the detriment of security, some nomenclators regressed to a modified two-part form. The code elements paralleled the plain in segments of a few dozen groups, but the segments themselves were in mixed order. For example, a Spanish nomenclator, a cifra general of 1677, has the syllables from bal to ble represented by the numbers from 131 to 149, but bli, following ble, is encoded by 322. This series continues to Bigueras at 343, while 150 reappears farther down the list as the codegroup for c.

  As he grew old, Rossignol retired to his country home at Juvisy though he reportedly continued to perform his special magic to the end of his life. His last days were brightened by an unmistakable demonstration of royal esteem: the Sun King made à detour in a progress back to Fontainebleau to visit him at Juvisy—this in an age when courtiers vied for the privilege of removing the king’s pajamas at grand and petit levees each morning! Rossignol died soon after, in December of 1682, only a few days short of his 83rd birthday on January 1.

  He had been the cryptologist of France in that incomparable moment when Molière was her dramatist, Pascal her philosopher, La Fontaine her fabulist, and the supreme autocrat of the world her monarch. Rossignol was, like them, a superlative practitioner of his art at the foremost court of Europe in the very splendor of its golden age.

  His work was carried on by his son, whom he had tutored. Bonaventure succeeded to his father’s 12,000 livres a year, and in 1688 was raised from counselor to the parlement to president of the Chamber of Accounts. A contemporary describes him as an “intriguer, very ugly, who has gained great well-being from deciphering letters.” He numbered among his friends the great letter writer, Madame de Sévigné. When he died, in 1705, the Marquis de Dangeau remarked in his Mémoires that he was the
finest decipherer in Europe. The Mercure Galant likewise praised him, saying that “the King himself admitted being vexed by his death: which alone may suffice for his eulogy.” Saint-Simon would only concede that “he became adept at it, but not to the point of his father. They were,” he summed up, “honest and unassuming men, who both waxed fat on the king, who even left a pension of 5,000 livres for those members of the family who were not old enough to decipher.” Bonaventure’s eldest son had been killed in an accident, and his second son, Antoine-Bonaventure, who had been destined for a career in the church, switched to what had become the family trade. He inherited the Rossignol acuity in cryptanalysis, and eventually succeeded his father as president of the Chamber of Accounts.

  One of the most important contributions of the Rossignols was to make crystal clear to the rulers of France the importance of cryptanalyzed dispatches in framing their policy. So effectively did their work demonstrate this that the war minister, Louvois, vigorously encouraged anyone who could provide such intelligence. On July 2, 1673, while Antoine Rossignol was still alive, Louvois ordered 200 écus remitted to one Vimbois “for having found the cipher,” and, four days later, 600 livres to one Sieur de La Tixeraudière for his solution. The next year, he thanked the Count of Nancre at the Flanders frontier for sending him an enemy cipher table, saying “that if the man of whom you speak can help you succeed [in solving some enciphered letters], you may assure him that His Majesty will grant him what he asks.” Still another of Louvois’ cryptanalysts was named Luillier. All these endeavors coalesced into a central black chamber, or Cabinet Noir, which regularly read the ciphered dispatches of foreign diplomats throughout the 1700s.

  These successes quickened the French appreciation of the need to prevent cryptanalysis of their own systems. Their precautionary measures included frequent changes and an ironclad control. In 1676, Louvois sent a dozen two-part nomenclators to the provincial governors, and a few months later followed them up with a detailed order of the king about how they were each to be placed into individual packets and carefully marked. In 1690, when Louis XIV again ordered a change in the chiffre général, Louvois instructed the governors to return the old tables and reminded them to use the homophones in the new nomenclator and not always to repeat the same cipher character. And in 1711, Louis, though a crabbed and tired old man then only four years from his grave, was ordering still another set of nomenclators sent to these governors. Extant records of the ministry of war for the reign of his successor, Louis XV, comprehend nomenclator after nomenclator, all of several hundred number groups in thoroughly disarranged fashion, for use with various individuals. One of several special “Canada Tables” was for the Marquis de Montcalm; it is dated 1755, just before that general sailed to defend New France against the British and to die a hero’s death in battle with Wolfe on the Plains of Abraham. In the repertory of a 1756 nomenclator, destined for France’s colonial efforts in Asia, the proper names of the East glow like rubies: the Mogul, the Nabob, Pondichéry, India itself. A note on another nomenclator, intended for use among ten persons, demonstrates the care with which they were used: “Suppressed,” reads the notation, “M. de Marainville having lost his.”

  The prudence was not excessive. One day near the end of Louis XV’s reign in 1774, a marshal of France brought a package from Vienna into the king’s presence. When Louis undid it, he was astonished to see not only dispatches of the king of Prussia to secret agents in Paris and Vienna, but also plaintext copies of his own most secret enciphered correspondence, and messages between the head of his spy organization and his ambassador in Stockholm, who participated in the coup that set up the strongly pro-French Gustavus III as absolute monarch of Sweden. Louis was told that the package had come from the Abbot Georgel, secretary to France’s ambassador to Austria. Georgel had met a masked man at midnight in Vienna and had been given the packet in return for 1,000 ducats. When he opened it in his room, he found that he could obtain twice weekly all the discoveries of the black chamber of Vienna, in which the correspondence of all powers was surreptitiously opened, solved, and read. Georgel made the deal, and continued to meet the mysterious agent at midnight, sending the documents to Louis twice a week by special courier.

  Black chambers were common during the 1700s, but that of Vienna—the Geheime Kabinets-Kanzlei—was reputed to be the best in all Europe.

  It ran with almost unbelievable efficiency. The bags of mail for delivery that morning to the embassies in Vienna were brought to the black chamber each day at 7 a.m. There the letters were opened by melting their seals with a candle. The order of the letters in an envelope was noted and the letters given to a subdirector. He read them and ordered the important parts copied. All the employees could write rapidly, and some knew shorthand. Long letters were dictated to save time, sometimes using four stenographers to a single letter. If a letter was in a language that he did not know, the subdirector gave it to a cabinet employee familiar with it. Two translators were always on hand. All European languages could be read, and when a new one was needed, an official learned it. Armenian, for example, took one cabinet polyglot only a few months to learn, and he was paid the usual 500 florins for his new knowledge. After copying, the letters were replaced in their envelopes in their original order and the envelopes resealed, using forged seals to impress the original wax. The letters were returned to the post office by 9:30 a.m.

  At 10 a.m., the mail that was passing through this crossroads of the continent arrived and was handled in the same way, though with less hurry because it was in transit. Usually it would be back in the post by 2 p.m., though sometimes it was kept as late as 7 p.m. At 11 a.m., interceptions made by the police for purposes of political surveillance arrived. And at 4 p.m., the couriers brought the letters that the embassies were sending out that day. These were back in the stream of communications by 6:30 p.m. Copied material was handed to the director of the cabinet, who excerpted information of special interest and routed it to the proper agencies, as police, army, or railway administration, and sent the mass of diplomatic material to the court. All told, the ten-man cabinet handled an average of between 80 and 100 letters a day.

  Astonishingly, their nimble fingers hardly ever stuffed letters into the wrong packet, despite the speed with which they worked. In one of the few recorded blunders, an intercepted letter to the Duke of Modena was erroneously resealed with the closely similar signet of Parma. When the duke noticed the substitution, he sent it to Parma with the wry note, “Not just me—you too.” Both states protested, but the Viennese greeted them with a blank stare, a shrug, and a bland profession of ignorance. Despite this, the existence of the black chamber was well known to the various delegates to the Austrian court, and was even tacitly acknowledged by the Austrians. When the British ambassador complained humorously that he was getting copies instead of his original correspondence, the chancellor replied coolly, “How clumsy these people are!”

  Enciphered correspondence was subjected to the usual cryptanalytic sweating process. The Viennese enjoyed remarkable success in this work. The French ambassador, who was apprised of its successes through Georgel’s purchases from the masked man, remarked in astonishment that “our ciphers of 1200 [groups] hold out only a little while against the ability of the Austrian decipherers.” He added that though he suggested new ways of ciphering and continual changes of ciphers, “I still find myself without secure means for the secrets I have to transmit to Constantinople, Stockholm, and St. Petersburg.”

  The Viennese owed at least some of their success to their progressive personnel policies. Except in emergencies, the cryptanalysts worked one week and took off one week—apparently to keep them from cracking under the intense mental strain of the work. Though the pay was not high, substantial bonuses were given for solutions. For example, bonuses totalling 3,730 florins were disbursed between March 1, 1780, and March 31, 1781, for the solution of 15 important keys. Perhaps the most important incentive was the prestige accorded to the cryptanalysts b
y direct royal recognition of their value. Karl VI personally handed the cryptanalysts their bonuses and thanked them for their work. Empress Maria Theresa conferred frequently with the officials of the black chamber about the cipher service and the cryptanalytic ability of other countries; that remarkable woman demonstrated her grasp of the principles involved by inquiring whether any of her ambassadors had corresponded too much in a single nomenclator and ought to be given a new key. The cryptanalysts sometimes even got paid for not solving a cipher: if a key was stolen from an embassy, the codebreakers would get a kind of unemployment compensation because they had no opportunity to win their bonus. In 1833, for example, the cabinet got three fifths of the solution bonus when the key of the French envoy was stealthily removed, copied, and replaced in a cupboard in the bedroom of the secretary of the French legation within a single night.

  The cryptanalysts’ training likewise aimed at stimulating extra effort. Young men about 20, of high moral caliber, who spoke French and Italian fluently and knew some algebra and elementary mathematics, were assigned to cryptanalysts as trainees. They were kept ignorant of the real work going on while they learned to construct keys, and then tested as to whether they could break the systems they had constructed. If they failed, they were transferred to another civil service job. If they proved competent, they were introduced to the secrets of the black chamber and sent to other countries for linguistic training. The starting salary was 400 florins a year, and this was doubled when they solved their first cipher. Their instructors were paid extra for the tutelage. Since all directors had to be cryptanalysts, this was the way for a young man to become director of the black chamber—a high-status post which paid salaries varying between the extraordinarily good rates of 4,000 and 8,000 florins, which often brought awards of such medals as the Order of St. Stephan, and which gave direct and frequent access to the monarch, with all that that privilege implied.