by DAVID KAHN
It increased the efficiency of the checkerboard by specifically giving the high-frequency letters the single digits. This cut down the length of the cryptograms and hence time on the air. Both Max Clausen, radio operator for the Sorge net, and Alexander Foote of the Swiss ring, enciphered in English, and consequently they used the eight most common letters of that language. They memorized them by the rather ominous phrase “a sin to er(r).” However, the sequence of those letters played no part in the construction of the key alphabet.
For that construction, a keyword was selected. Clausen used SUBWAY. The encipherer wrote this out, followed by the rest of the alphabet in rows beneath it, with a full stop and a letter-number switch sign at the end. Then the digits 0 to 7 were assigned to ASINTOER as they occurred vertically in columns from left to right. Finally the two-digit groups from 80 to 99 were assigned to the remaining letters and symbols, also vertically:
These equivalents can be placed into the more compact checkerboard:
The encipherer next replaced his plaintext with his checkerboard equivalents. For numbers, he enciphered the switch sign, then repeated the digits twice, then enciphered the switch sign again to indicate a return to letters:
The next step enshrouded this simple text by adding a numerical key—an operation called “closing.” Clausen and Foote took their keynumbers directly from a common reference book with many tables, like the World Almanac, possession of which would not necessarily be suspicious. Foote used a book of Swiss trade statistics, Clausen the 1935 edition of the Statistisches Jahrbuch für das Deutches Reich—the main section, on white pages, for enciphering, the international survey section, on separately numbered green-tinted pages in the rear, for deciphering.
The message requesting information about the 106th Division resembles one actually sent to the Sorge ring on March 3, 1940. Since Clausen would be deciphering it, it was enciphered in Moscow with an additive from the green pages of the Statistisches Jahrbuch. The encipherer picked at random the group at the 11th row in the 3rd column of page 171. That group happens to give the thousands of metric tons of foundry products fabricated for railroad construction in Luxembourg in 1931, which was 113. The encipherer began, as an enciphering rule required, with the third digit, 3, and then ran along that line in the table, taking his other keydigits from the production figures for Belgium, France, Great Britain, and so on for 1931 and succeeding years: 134, 534, 517, and so on. These digits he wrote beneath the checkerboard encipherment and added them with noncarrying addition to produce the cipher:
The encipherer divided this into groups of five, 22228 77616 59412 47033 42932 8964, with perhaps a 0 at the end to fill out the group. He then composed an indicator group to tell the decipherer where to find the key: 11 for the row, 3 for the column, 71 for the page (hundreds figures were omitted; presumably the decipherer would have to try page 71 or 271 if page 171’s key did not make sense). To conceal this indicator group, 11371, the encipherer added to it, by noncarrying addition, the fourth group from the beginning of the message, 47033, and the fourth group from the end, 59412, to give 07716. He placed this group at the head of the message and gave it to the radioman to send.
This was the standard Soviet spy cipher of World War II. Later in the war, when Foote was enciphering, a few minor improvements had been made to improve reliability and security. Numbers were repeated three times instead of twice. Instead of just one enciphered indicator group, two were used. Foote composed them by adding the plain page-column-line indicator to a fixed group (his was 69696) and then, for the first enciphered indicator, he added this sum to the fifth ciphertext group from the beginning, and, for the second, to the fifth ciphertext group from the end. He then inserted these enciphered indicator groups as the third group and the third from last group of the final cryptogram.
Other Soviet spies, however, used a variation of this basic system that was both more complicated and less secure. It generated the key digits from the text of an ordinary book by enciphering that text in a checkerboard. The Rote Kapelle used this variation (when the Germans discovered one of the keybooks, a unit of the Rote Kapelle wirelessed, “Klaus has the Bible”). So did some members of Foote’s Swiss ring, who used Es geschah im September (“It Happened in September”), and Bertil E. G. Eriksson, a Soviet spy arrested in Sweden in 1941, who used a 1940 Swedish edition of Jaroslav Hasek’s The Good Soldier Schweik.
The first words of Eriksson’s keytext also served to construct his keying checkerboard. For one such construction, Eriksson chose to begin at page 12, line 3, word 4: “PAUS, SOM SVEJK SJÄLV AVBRÖT….” He inscribed the first ten different letters into a straddling checkerboard as its first line and followed them on other rows with the remaining letters of the alphabet. He then produced a numerical key for the top coordinates by numbering the letters in the top row from 0 to 9 according to their alphabetical position. The first line was given no side coordinates; the two other lines got their coordinates from those standing above the first and last blank spaces in the last line. The result:
He then began his keytext with the third letter of the first word of the keyline, and enciphered Hasek’s words to produce his additive: “[DE]T BLEV EN PAUS, SOM SVEJK SJÄLV AVBRÖT MED …” became 30 96 91 1 9 1 92 6 08775479123720 91 909 96 365 30 41 98 …. Eriksson added this to a numerical plaintext produced via a Russian straddling checkerboard of 35 cells based on the keyword GAMBUSIA (a genus of minnows) and with seven high-frequency Russian letters given single digits.
Soviet spy Bertil E. G. Eriksson enciphers a message for Moscow in 1941. The upper line is the additive key, produced by enciphering through a straddling checkerboard a text beginning at page 12, line 3, word 1, letter 3, of a 1940 Swedish edition of Jaroslav Hasek’s The Good Soldier Schweik; the lower line is the plaintext, in Russian, based on a straddling checkerboard with key GAMBUS1A
This variant of the standard system is not unbreakable. The use of a coherent keytext gives the cryptanalyst a leverage which enables him to mutually recover both it and the plaintext. The straddling feature, the irregular lengths of the plain and key elements, destroys the ordinary one-to-one correspondence between plain, cipher, and key and makes his work more difficult than if an ordinary checkerboard had been used; nevertheless, solution is possible. It is probably not possible analytically with trade statistics as a key. Though such keys are not ideal because they may contain certain regularities owing to recurrent annual figures and because they are public, they certainly offer adequate security.
How did this standard Soviet system, so simple but so strong, serve Russia during World War II?
Dr. Richard Sorge, a tall, stocky man with malevolent eyes, worked in Japan as a correspondent for Germany’s finest newspaper, the Frankfurter Zeitung. A member of the Nazi party, he was an intimate of the German ambassador, Eugen Ott, with whom he had been friends since Ott had been assistant military attaché. Sorge even served as press attache for the German embassy, and, while breakfasting with Ott, read and discussed papers and policies with him. Then he passed this high-level intelligence to Germany’s avowed enemy, the Soviet Union. For the efficient Germans had somehow failed to discover that Sorge’s grandfather had been secretary to Karl Marx and that he himself was a dedicated Communist.
Sorge had directed a Soviet spy ring in Shanghai from 1929 to 1931, and the ability he had demonstrated, plus his interest in the Far East, caused the G.R.U. to send him to Japan two years later under his journalistic cover. His assignment was to ascertain the intentions of Japan, Russia’s former enemy and only rival in the Western Pacific and holder of an Oriental dagger that she could plunge into Russia’s back. Sorge painstakingly built up his own contacts and recruited agents among the Japanese. His most important catch was Hotsumi Ozaki, who was a kind of Harry Hopkins to Prince Konoye, thrice premier of Japan. Sorge thus had a direct pipeline into the highest councils of the Japanese government, while he himself had access to the best information and opinions of Japan’s ally. In addition, more
than two dozen other Japanese supplied important bits of military and economic intelligence.
Sorge sent this information to Russia by film through couriers and by radio. His radio operator was Max G. F. Clausen, a heavy-set German with pleasant features and curly hair who had served as a radioman in the German signal corps during World War I and had worked with Sorge in Shanghai. As cover, he sold machinery for blueprint reproduction in a private enterprise that was so phenomenally successful that it severely shook his faith in Communism: in 1941, he sent only a third of the messages that Sorge gave him. But at first he performed miracles in establishing and maintaining radio contact over very long distances with a portable transmitter that he had built himself. He set it up for sending, and dismantled it and carried it away in a large briefcase after each transmission. This almost backfired one night when he and another agent had the radio in its case with them and were stopped by a policeman. “My heart jumped at the thought that we had been discovered,” he wrote. “For some reason or other, the policeman merely remarked, ‘Your headlights are out; be careful,’ and walked away without examining our baggage or searching us.”
With the approach of war, the Sorge ring accelerated its communications. Transmissions, which had been made irregularly, began in 1938 to be made regularly: on odd days and Sundays at 3 p.m. and the following mornings at 10. Clausen sent to a Russian station codenamed WIESBADEN, which he thought was probably in Vladivostok, possibly in Khabarovsk or Komsomolsk; the messages were relayed from there to Moscow. At first Clausen merely transmitted already coded messages, but after Sorge was in a motorcycle accident in 1938, he obtained permission from Moscow to teach Clausen the cipher system.
“I always encoded and decoded at my home in a room used only by myself,” the radio operator wrote. “Usually I was warned of visitors by the ring of the doorbell so that I could clean up my papers before receiving them. On three occasions, my Japanese employees saw the code but did not seem to pay any attention to it. Once, when I was in bed [this appears to refer to his being bedridden from April to August, 1941, by a heart ailment] and encoding a message (employing a special board which enabled me to work in a reclining position), Dr. Wurtz, who was always shown in by the maid, suddenly appeared at my bedside alone. He glanced down at the code chart suspiciously but merely said, ‘You must not do any writing until you get well,’ went through a routine checkup, and departed. For several days I was afraid that he might have informed the police, but nothing came of it.” His messages went out in English, sometimes German, never Russian—to conceal the true allegiance of the ring.
Sorge had discovered not only that Germany was planning to attack Russia, but also the approximate date. Stalin ignored the information, as he had other invasion tips, and was taken by surprise. With the war on, the moment for which Sorge and his ring had prepared ever since their arrival in Japan was at hand. They bent every effort to discover the one piece of information that both Sorge and the Soviet government considered the most vital to Russia’s conduct of the war, perhaps, in fact, to her very existence: Would Japan attack Russia at this moment of weakness and “shake hands with Hitler in the Urals,” or would she pursue her already well-laid plans to conquer Malaya and the Dutch East Indies with their rubber and oil? Japan made her decision in deepest secrecy at a cabinet meeting of July 2 in the presence of the Emperor. As hints and portions of it leaked out, the ring sent Russia increasing amounts of information.
In 1939, Clausen sent 23,139 cipher groups, in 1940, 29,179, and though, in 1941, increasingly disillusioned with Communism, he sent only 13,301, Sorge more than took up the slack, himself sending 40,000 groups. Much of this traffic was intercepted by Japanese counterespionage police. The Communications Ministry, the Tokyo Metropolitan Communications Bureau, the Osaka Communications Bureau, and the Communications Bureau of the Governor General of Korea had all been aware since at least 1938 that an illegal radio was transmitting from the Tokyo area. Japanese cryptanalysts failed utterly to solve the messages, and their radio policemen failed equally to locate the clandestine transmitter. These two failures precluded the Japanese both from rounding up the ring and from feeding it false information.
Various political considerations made it gradually clearer to Sorge that Japan had decided against marching to meet Hitler. Throughout the summer, as German columns rolled across the steppes, he communicated these developments to Moscow. Finally, Ozaki confirmed the decision for the southward advance and against war with Russia, and, early in October, Sorge reported his final sober conclusion: “There will be no attack until the spring of next year at the earliest.” The Soviet Union had begun drawing troops from its eastern reservoirs of manpower as Sorge’s reports grew increasingly optimistic. Now, just as his definitive message was reaching Moscow, the Germans launched an all-out two-pronged attack to capture the Russian capital before winter.
The Red command, no longer fearing a Japanese stab in the back, reduced its Far Eastern garrison by 15 infantry and 3 cavalry divisions and by 1,700 tanks and 1,500 planes. It transported these troops, which Germany thought it could not possibly possess, across the biggest country in the world to its Western Front. These fresh troops, plus the worsening winter, slowed the German advance, but the Germans repeatedly punched holes in the horseshoe of the city’s defenses with “fists” of massed armor. On December 2, they reached the suburb of Khimki: in the distance, the onion domes of the Kremlin cathedrals pricked the leaden sky! The next day, Marshal Georgi Zhukov flung his newly arrived reserves into a furious counterattack, and, aided by weather 13 degrees below zero, drove the half-frozen Nazis back. Within five days, Berlin announced the suspension of the eastern offensive. Moscow had not fallen. The ikon of Holy Russia still stood.
Not so Sorge. A Japanese who was not in his ring had been arrested on suspicion of Communist activities. To ingratiate himself, he told of suspicious activities by a woman who was a member of the ring. Her confession led, through a long chain, to the arrest of Ozaki on October 15 and of Sorge and Clausen on the 18th. Clausen broke down under interrogation and disclosed the cipher system; the Japanese, finally able to read the tantalizing messages, produced them as damning evidence in the trial. Clausen was sentenced to life imprisonment. Ozaki and Sorge were hanged 50 minutes apart on November 7, 1944. But, more than most men, they had fulfilled their missions.
Perhaps the most widespread of the Soviet networks was one the Germans called the Rote Kapelle (the “Red Orchestra”). Its tentacles slithered into the most secret tabernacles of Naziism, and its loose ramifications covered much of Germany and occupied Europe. It derived its name from the steady hum of the “music boxes”—Soviet term for radio transmitters—in Berlin, Paris, Brussels, Ostend, Marseilles and elsewhere that piped out the coded information of 300 agents. Its maestro was Harro Schulze-Boysen, a Luftwaffe lieutenant in the Forschungsamt who came from an impeccable German family that included Admiral von Tirpitz; he had himself moved gradually from a conservative anti-Naziism to pro-Communism. Concertmaster was the fortyish Arvid Harnack, nephew of the influential theological historian, Adolf von Harnack. And the manager was Leopold Trepper, “grand chef” of Soviet espionage in the West, a professional spy director who had established himself at Paris under the cover of the Simex Corporation.
The organization that he built up under Schulze-Boysen and Harnack remained latent until the Germans crossed the border on June 22, 1941. Instantly Moscow demanded information on German plans. The Rote Kapelle sprang to life. Soon the cricketlike chorus of its Morse transmitters filled the ether with their incessant chirpings of five-digit groups.
In Cranz, in East Prussia, the antennae of the Funkabwehr, the Nazi radio counterespionage, quivered. The first message was intercepted June 26. Attempts to solve it and those that followed failed. Tracking down the transmitters themselves was hindered by a shortage of equipment: the Funkabwehr then had only six long-range direction-finders. Not until October did it ascertain that Moscow was receipting for the mess
ages. Not until December did it pinpoint its first Rote Kapelle station. On the night of the 13th, a troop of soldiers wearing socks over their boots silently climbed to the second floor of a villa at 101 Rue des Attrebates in Brussels. They broke into the radio room and arrested the cryptographer-radioman, Mikhail Makarov, a Russian Air Force lieutenant and a relative of Soviet Foreign Minister Vyacheslav Molotov, and two other agents. At this very moment, Trepper himself arrived. But with superhuman aplomb, he passed himself off as—of all things—a rabbit vendor, and was not apprehended.
The Germans also found in the fireplace of the villa a charred piece of paper covered with numbers; it was obviously an enciphering worksheet. German cryptanalysts immediately began to study it. Makarov refused to talk, and it was not until six weeks later that the first significant information emerged. It was part of a sentence in French that seemed more like a fragment of keytext than of plaintext, and it contained the word PROCTOR. The Funkabwehr questioned the landlady, a naïve elderly widow, who named eleven books that she had seen her tenants reading. In Le miracle du Professeur Wolmar, a 286-page science-fiction novel by Guy de Teramond, the Nazis found PROCTOR.
Suddenly the Germans saw the magnitude of what they were faced with. The Teramond key unlocked 120 messages of what had been the busiest Rote Kapelle station. These had warned Moscow of Germany’s spring offensive in the Caucasus, reported on Luftwaffe strength, provided data on army fuel consumption and casualties, and furnished similar other vital information. But all names were codenames; the three arrested agents either would not or could not give links to the rest of the network. The Funkabwehr redoubled its efforts.
Trepper, however, after his melodramatic evasion, had alerted the other members of the Rote Kapelle. Couriers brought them new keys. Soon the orchestra was playing with renewed volume. Many of the numbers were requests by Moscow:
