Cracking It

The silk of Leo Marks’ mesmerizing book is exactly that--a square piece of silk covered with printed material for encoding messages. It was part of the equipment carried by the heroic men and women, native speakers or Britons who could pass as such, who were infiltrated, by parachute or light aircraft, into countries occupied by the Germans between 1940 and 1945. They went in wearing civilian clothes, with faked ID papers and radio equipment. Their messages would be intercepted and recorded by German counter-intelligence, but because the basis for the code would alter from one message to the next (and the portion of the silk used would be destroyed by the agent) there was little chance that the message would be deciphered. Furthermore, the silk, unlike the bulky one-time pads that served the same purpose, would pass undetected in the frequent random body searches carried out by German police in the occupied cities. Cyanide was the agent’s last resort if identification as an agent seemed inevitable; the alternative was to face torture and death or else to send misleading messages under German direction.

Marks, son of the founder-owner of the famous bookshop at 84 Charing Cross Road, has been fascinated by codes and code breaking since childhood. At his first test given to job applicants with Special Operations Executive or SOE, he astonished his examiners by decoding the message without using the code, which had been given to him but which he had not noticed. He was soon in charge of a staff of young women in uniform who deciphered the messages coming in from Europe. It was a fiendishly difficult task, because the agents, enciphering under pressure and transmitting in haste (for German direction-finding trucks would be pinpointing sources of signals) often made mistakes in both operations, producing what was known in the trade as an “indecipherable.” It often took many many hours, and as many brains, to extract sense from the resulting jumble.

When Marks arrived at SOE, most of the agents were using as the basis for their code a poem that they knew by heart. This had the advantage that the only clue to the agent’s code was in her or his head; the disadvantage was that the poem was quite likely to be known to the German code-breakers and the slightest breakthrough might lead them to the full solution. One agent, for example, had chosen the British national anthem, another Rupert Brooke’s famous lines “If I should die, think only this of me. . . .” Marks was determined to find something better and hit on the idea of the silk but had a hard time convincing his superiors of its value. In the final interview that resulted in approval, he was told that it would be a great help if he could just jot down on a half sheet of paper the difference it would make for the agents. He announced that it could be done in a phrase. Challenged to produce it, he replied: “It’s between silk and cyanide.” By the summer of 1943, the silks were ready for use.

Meanwhile the agents continued to use poems. Marks suggested that they write their own and to those who could not, he offered poems of his own composition. He also encouraged his code-breaking ladies to contribute, with the result that one day a superior officer of their organization on an inspection tour stumbled on a pile of their poems. Among them was a hilarious and very explicit ode on the private parts of Gen. Charles de Gaulle. He was SOE’s be^te noire because he insisted that all the agents sent in by his organization use a secret French code. (It was later broken by Marks.)

Some of Marks’ poems that were actually used by agents are printed in the book. They are, as they had to be, easy to remember, and some are hard to forget, especially the poem [see page 7] he prints as part of the book’s dedication, which begins: “In December 1943 I wrote a poem which I gave to Violette Szabo to use as a code. This book is dedicated to all those who shared it with her.” She was a young agent whose charm and beauty dazzled him when he briefed her on her codes before she left for France in April 1944. She was captured in June after holding off some troopers of Das Reich Division with a Sten gun to give her companion a chance to escape. She was executed in April 1945, a few weeks before the German surrender. At Ravensbruck she “had knelt down, holding hands with Lilian Rolfe and Denise Bloch, and been shot in the back of the head.” At Dachau “Noor [another charming woman whom he had briefed] . . . had also knelt down, and Yolande Beckman, Madelaine Damerment and Eliane Plewman had crossed the bridge with her. Vera Leigh, Diana Rowden and Andree Borell had been given lethal injections at Natzweiler, and Yvonne Rudellat had been buried at Belsen.”

There were many others too, heroic men as well as women, who gave their lives, but it was not in vain. The information they sent back identified targets for the bombers and shaped the preparations for D-Day; their radio contact made possible the arming of the maquis and the dispatch of uniformed Allied teams such as the Jedburghs and the Special Air Service that went in on and after D-Day. Some of their successes were spectacular, like the destruction of the heavy water plant at Rjukan in Norway, a feat that crippled the German program for producing atomic weapons. But there was one tragic failure--the capture of an agent in Holland who was forced to work under German supervision. His home base failed to recognize the secret signals that he was sending under German direction. The consequence was the dispatch of more agents and important figures of the Dutch resistance, all of whom fell into German hands. Marks had been suspicious of the agent’s messages early on because they were not “indecipherables”; every word was enciphered and transmitted faultlessly. But he was unable to convince others, and the sad story continued until it became crystal clear that he was right. At which point the German in charge sent a mocking message in the clear thanking them and assuring them that they would get a warm welcome if they ever came to visit.

Marks was a civilian working for a military bureaucracy, a youth (by the end of the war he was “crowding 23 and frequently mistaken for an adult”) who seemed delighted to take every opportunity to challenge his elders, a Jew in a predominantly Gentile organization. He was also the possessor of an acerbic wit and a fine sense of the ridiculous as well as a fanatic devotion to the interests of the heroic agents whom he served, assets that helped him through many a crisis. They are also in play in this absorbing account of his career as a code-breaker, which handles with equal effectiveness the comic and the tragic elements of his tale.

*

Simon Singh, the author of “Fermat’s Enigma,” deals in his new book not only with the Enigma coding machine of Hitler’s armed forces but also with the history of codes and their breaking from the beginning to the present day, ending with some informed speculation about their future. They began in the ancient world with a simple system of substitution of one letter of the alphabet for another according to a previously established pattern to shift three places to the right, for example, so that A would become D and Z would appear as C. This is known as the “Caesar shift” because it was the favorite military cipher of Julius Caesar. It was the prevailing method for most of the first millennium though al-Kindi, the “philosopher of the Arabs,” had explained how to decipher it some time in the 9th century. His method was frequency analysis: If you know which letters occur most often in the language of the message (E, T, A and O in that order in English) you can soon pick them out in an encoded message of a respectable length. You can also spot frequent combinations of letters, such as H and E in English--the, she, then, there, etc.--and will soon be on your way to a complete solution. Singh takes the reader through the complete process of deciphering a seven-line message of this type.

By the 16th century, the method was well known in Europe, and efforts were made to complicate the encoding process. But the code-breakers kept up with new developments. Venice, for example, was famous for the skill of its cryptanalyst Giovanni Soro, who was often called on for help by other states, including the Vatican. Spain, however, lagged behind in the race, and when Philip II finally realized that the French expert Francoise Viete had been reading all his traffic, he called on the pope to try Viete before a papal court as a sorcerer in league with the devil. Another victim of decryption was Mary, Queen of Scots, whose encouraging letter to the Babington conspirators, who were plotting to kill Elizabeth I, was deciphered by Sir Francis Walsingham, Elizabeth’s combined FBI and CIA, and served as the crucial evidence that brought her to the headsman’s block.

Singh pursues the fascinating story through the centuries, always providing plenty of detailed examples of ciphers for those who appreciate the intricacies of the medium. He explains the “indecipherable cipher” of Vigeniere, which is a substitution code that uses not one alphabet but 26. It was finally broken by the 19th century English eccentric Charles Babbage who also “developed the blueprint for the first computer.” Singh introduces the reader to the full text of a cipher that conceals the whereabouts in Virginia of a treasure that was buried in the 1820s by a man named Beale that would now be worth $20 million. Many have tried to break it, and some have gone on to dig (one as recently as the 1970s), but the treasure (unless the whole thing was a hoax) is still there.

In World War I, the British and French were able to read the German codes; perhaps the most spectacular advantage accruing from this was America’s entry into the war on the Allied side, precipitated by the revelations of the “Zimmermann note” about an escalation of submarine warfare. The German general staff did not realize that the Allies had been reading their codes until they read about it in Churchill’s history of the war, whereupon they took steps to ensure that it would not happen again. For Hitler’s war, they developed the Enigma machine; Singh explains its complicated operations in a lucid text helped out by diagrams. He also chronicles the exciting tale of its defeat by Polish and British experts that led to the establishment of the code-breaking crew of mathematicians, physicists (among them Alan Turing) and linguists at Bletchley, where they read German army, navy and air force traffic all through the war.

Singh ends by charting the impressive advances made in the field since the war and tries to imagine its future. Will the expected invention of the quantum computer finally make possible an unbreakable code? Has the computer perhaps already been invented and the information classified? Singh discusses too the problem of the protection of privacy in e-mail and on the Internet, a growing concern for the individual as well as for business and the likelihood of government opposition to encryption as a limitation on its ability to monitor communications in its fight against crime, espionage and terrorism. *