April 1973 | Volume 24, Issue 3
THE MAKING AND BREAKING OF CODES AND CIPHERS HAS PLAYED AN EXCITING AND OFTEN CRUCIAL PART IN AMERICAN HISTORY
By choice, cryptographers are an unsung and anonymous lot. In war and peace they labor in their black chambers, behind barred doors, dispatching sheets of secret symbols and reading encoded messages from the innermost councils of foreign governments. Few tales have leaked from those rooms.
Yet cryptographers have at critical moments affected the tide of history, for better or for worse, far more than some of the legendary heroes known to every schoolboy. On occasion American officials have blundered badly with codes and ciphers. On other occasions American cipher experts have shown brilliant flashes of imagination that lone will live in the sparse annals of cryptography.
Such unsung heroes were on Admiral Chester Nimitz’s intelligence staff in the Pacific at a highly critical moment in the spring of 1942. Radio monitors were intercepting a heavy volume of traffic from all elements of the Japanese fleet. Some of the messages were deciphered, and it became increasingly evident that Admiral Isoroku Yamamoto (who one year later was to die because a deciphered message had pinpointed the route of his airplane flight) was planning the biggest naval operation of the war. Nimitz had scant forces to oppose such an operation.
The key question at Pearl Harbor was Yamamoto’s target, knowledge of which was crucial to the planning of any effective counterstrategy. The deciphered messages referred to the target only as “ AF .” Was AF Midway ?Nimitz thought so but couldn’t be sure. Was AF Pearl Harbor itself? Admiral King, Nimitz’s superior back in Washington, thought so. How could AF be identified?
At this point Nimitz’s intelligence staff evolved a simple but ingenious plan to bait the Japanese into revealing the target themselves—and the heart of the plan was a unique exercise in cryptography. An encoded message was sent to the American commander at Midway, ordering him to send back a fake message in the clear . This message was to state only that the water-distillation system for the atoll had broken down. The plan showed a delicate sense of judgment; if Midway was indeed AF , the water supply on the island was of military significance; yet the information about the distillation system was fairly routine, might well be sent in the clear, and thus would not arouse the suspicions of Japanese intelligence monitors. Midway dutifully transmitted the message.
A few days later intelligence officers at Pearl Harbor deciphered a Japanese transmission noting that AF was low on water.
Nimitz himself later noted that effective intelligence was a key factor in his victory over a vastly superior force. Knowledge of the target enabled him to move three carriers to the scene in time to surprise Yamamoto. The intelligence ruse was a striking innovation in cryptography. Nimitz’s staff used a message from Midway in the clear to lure Yamamoto into revealing the identity of his target in code . History has seldom noted such triumphs of codes, or ciphers, or the men who manipulate them. We shall never know the countless times that, thanks to cryptographers, vital messages have been transmitted in complete secrecy. A successful cryptographer is far more reticent about revealing his legerdemain than a Houdini ; he may want to use the same system again, and the course of a nation may depend upon it. In the history of American cryptography only one man has talked, perhaps in vengeance when the doors of his beloved black chamber were abruptly closed by government order. Yet despite their bars and bolts, the doors of those chambers beckon invitingly. Most of us, from the time we developed a secret language for our childhood club or wrote enciphered messages to our first love, have found fascination in codes and ciphers. Americans watched enthralled as Marlene Dietrich, in Dishonored , played a series of piano chords, thus transmitting the disposition of enemy troops in a musical cipher—despite the fact that only one real musical cipher has ever been developed, by English writer Philip Thicknesse, and it was unsatisfactory because information couldn’t be fashioned into anything that sounded like a tune. Detective literature abounds in the use of secret ciphers (remember the chilling moments as Sherlock Holmes unravelled the secret of the Dancing Men?), and on television a criminal or a government agent frequently uses an “unbreakable code” to achieve his despicable or laudable goal.
Despite our fascination, we Americans have until recently been reluctant to use codes and ciphers in official dealings and frequently have bumbled in our attempts. Perhaps there is something about secret writing that runs cross-grain to the necessary openness of a democracy.
One of America’s most eminent public servants took such a view. Henry L. Stimson personally destroyed the only peacetime American black chamber that existed prior to the power politics of the late 1930’s. Known as MI-8, the black chamber was founded by the egocentric Herbert O. Yardley in 1917 and continued to do effective work until 1929, when Stimson moved into his office as the new Secretary of State. Almost immediately a batch of decoded and deciphered messages, intercepted from foreign governments, crossed his desk. The irate Stimson demanded to know where the messages came from, and was told of Yardley’s cryptographic bureau, which then operated out of a four-story brownstone in New York’s East Thirties. The new Secretary of State ordered such nefarious business stopped immediately and refused to allot one penny of the State Department’s budget for further activities of this type.
Perhaps in a fit of pique, Major Yardley wrote a self-oriented book titled The American Black Chamber (1931) and thus became one of the few cryptographers to tell tales outside the walls of his workroom. He described in detail the work of MI-8 for some twelve years. Proudly he revealed that during World War I, in addition to espionage messages, the bureau had read more than ten thousand diplomatic telegrams sent by Argentina, Brazil, Chile, Costa Rica, Cuba, Germany, Mexico, Panama, and Spain.
Further, he stated that prior to the Washington Naval Conference of 1922 he had personally undertaken the cracking of the Japanese diplomatic cipher and even described how he went about it. As a result of his success American negotiators were well aware during the conference that although the Japanese were pressing insistently fora naval ratio of 10 to 7, they had already decided they would settle for a ratio of 10 to 6 if necessary. The Americans and British only had to wait them out. As Yardley observed, it’s not very difficult to win at stud poker when you know your opponent’s hole card.
Another Secretary of State had an equally difficult time deciding what to do about enciphered messages, and as a result the United States still owes a bill of $23,000, not counting interest since 1866.
In that year the first successful transatlantic cable was completed (a previous cable had broken almost immediately) . It was laid by an international company with a British board of directors, and the president of the company promptly called on Secretary of State William Henry Seward. The purpose of his call was to urge the use of the cable by the United States government for sending diplomatic messages. With the government as a customer the company could more easily persuade American businessmen that the cable was an effective means of instant communication. As any salesman knows, there is a right time and a wrong time to make a call, and in this case, by coincidence, the president of the cable company chose precisely the right time, for Seward had an urgent message to transmit to the American embassy in Paris. Two years previously Napoleon III had established Maximilian on the throne of Mexico. The United States, embroiled to the point of exhaustion in the Civil War, could make no effective pro- test. Now Seward was determined to reassert the Monroe Doctrine. As a gesture that the United States meant business, fifty thousand veteran troops under General Phil Sheridan had been dispatched to the Texas-Mexico border. Seward wanted to instruct his ambassador in Paris to impress upon the French government that these troops were only a sample of the armed host that would move toward Mexico if the French troops did not leave the continent.
It was a message of power politics, and for that reason its contents had to be kept secret. Seward decided to entrust the message to the transatlantic cable but to transmit it in the American diplomatic cipher, although he failed to mention this to the president of the cable company. There was some haggling over price. Finally the businessman agreed to transmit urgent government messages for “a very reasonable figure” under the regular price, which was ten dollars per word.
Seward’s enciphered message to his ambassador consisted of approximately eleven hundred groups of three-, four-, and five-digit numbers. In Paris it was deciphered, and Napoleon III was informed of the United States government’s opposition to the French adventure, a determined opposition backed by the threat of power. Napoleon found it expedient to recall his troops.
However, the bill for the enciphered message was another matter. When it reached Seward’s desk, the Secretary of State exploded; it was for $23,000. He demanded that the president of the cable company appear in his office and asked him what kind of usury the company was attempting to practice against the United States government. The man stood his ground, insisting that the bill was reasonable. He pointed out that the British directors of the company felt there was something not quite ethical about transmitting messages in a secret cipher. Only the cable layer himself, Cyrus W. Field, had been able to persuade them to transmit the message. In order to discourage the use of secret codes and ciphers in the future, the company was billing for such messages at double the normal rate.
Angrily, Seward pointed out that there were eleven hundred groups of digits, that the standard rate to anyone without the promised discount would be ten dollars per word, and that even if this price was doubled, it came to $22,000 instead of $23,000. What about that extra thousand dollars?
The cable chief patiently explained that because his firm had no way of knowing what each digit stood for, it had been decided that each digit, instead of a group, should represent a full word. There were 4,600 digits in the message, and he had been instructed to double the bill because it was in cipher. Therefore the bill really should be $92,000. However, with considerable reluctance his company was charging only one-fourth the figure it should charge and therefore had billed $23,000.
Seward accused the cable chief of dishonesty and unethical business practices and announced flatly that the United States government refused to pay the bill. Apparently it hasn’t been paid to this day.
Still another Secretary of State—and subsequent President—also had difficulties with ciphered messages. At the time of the Revolution there apparently was little knowledge of codes and ciphers in the colonies, and not much enthusiasm for their use. One exception was James Madison, who set up a personal cipher for his private correspondence with Edmund Randolph. It was a fairly simple transposition cipher, in which a key word was written, followed by a table of alphabets. The key word effectively jumbled the characters —too effectively in this case. Madison wrote Randolph: “The key will be the name of a certain black servant boy who used to wait on Mr. James Madison.” The servant’s name was Cupid. Although Madison was fascinated by ciphers, he was careless in enciphering. His correspondence with Randolph was so full of errors, resulting in a meaningless jumble of letters, that Randolph finally wrote in desperation, asking him to repeat his messages in plain English. According to Fletcher Pratt, America’s foremost authority on the history of ciphers, not even modern cryptographers have been able to track down some of Madison’s errors in order to decipher the messages and find out exactly what our fourth President intended to say.
The first official diplomatic code of the nation was prepared in 1789, probably with the help of French experts. It was a fairly elaborate code even by today’s standards, containing sixteen hundred numbers plus other characters. Since no diplomatic disasters were blamed on the code, it apparently was used effectively for about twentyfive years before it fell into disuse simply because, after 1815, the world situation permitted secret messages to be carried safely in diplomatic pouches.
It was an American who touched off a worldwide revival in the use of codes and ciphers. When Samuel F. B. Morse invented the telegraph, he not only made it possible for the ultimate commander, whether in diplomatic or military maneuvers, to retain personal command through instant communication, but he also threw those communications open to the public, since anyone could acquire the skill to intercept and read messages flowing through telegraph wires. Effective codes and ciphers became a necessity.
Edgar Allan Poe was attracted to ciphers when he heard of the abortive attempt of 1821 to return the Bourbons to the French throne, an attempt that depended to a large degree on enciphered correspondence and that failed because the cipher was broken. Poe’s interest flared, and he read everything he could find on codes and ciphers. It was inevitable that they would show up in his work. In 1840, in an article in a Philadelphia weekly, he published his famous claim that there was no such thing as an unbreakable cipher and offered to decipher any messages submitted by readers. Cryptographers note, however, that he hedged his claim. The message had to be in English, it had to involve no more than a simple substitution cipher, and it had to preserve the word divisions of the clear. It is obvious that Poe was a good amateur cryptanalyst, for he solved all of the hundred-odd messages that arrived as a result of his offer. It is also obvious that he was only a selftaught amateur, for the diplomatic and military ciphers of his day were far more difficult than the ciphers his rules permitted. His frequency tables, which he probably developed himself, were quite inaccurate.
However, Poe, more than any other human being, aroused the interest of the world in cryptography and cryptograms. Who, even today, can read “The Gold Bug” without the thrill of intellectual discovery as the message gradually and logically is deciphered in front of his eyes? Other writers, including Jules Verne and Balzac, responded to Poe’s interest and soon were weaving cryptograms into their fiction.
Paralleling the literary interest was the resurgence of interest in professional cryptography, and this probably worked to the advantage of the North during the Civil War. Although the South developed highly effective cavalry raiders who were adept at tapping telegraph wires, it had few trained cryptographers to decipher the abundance of intercepted Union messages. The North, on the other hand, obtained only meager enciphered material from the enemy but had some excellent cryptographers. Perhaps their greatest work was the decipherment of the Cammack letter.
In December of 1863, in New York City, the postmaster intercepted a letter addressed to A. Keith in Halifax, Nova Scotia. Since that address was a known center of Confederate espionage, the letter was opened. It contained a message in a design cipher partially based on the Rosicrucian cipher. However, there were four other types of characters in the cipher. The message was turned over to three Army cryptographers.
Although the cipher appeared difficult to solve on the basis of only one message, there were vulnerable points, and the cryptographers seized upon these. Despite the fact that the message was in cipher, it had been written in the format of an ordinary letter. Quite obviously a date had been placed in the upper right-hand corner, a salutation was indicated, and a signature was affixed. In addition, two words, “reaches you,” had been written in the clear in the middle of the message. This was a critical weakness and the key to the attack, for it enabled the cryptographers to make a series of guesses as to the preceding words, then test them to see whether the resulting relationships of symbols to clear made sense elsewhere in the message. Their logical guess that the entire phrase might be “before this reaches you” struck pay dirt. With this as their lever they rapidly pried loose other symbols, and very soon the cipher fell apart.
The point of the message was that “12,000 rifled muskets came duly to hand and were shipped to Halifax as instructed.” The note ended with a plea for more money and was siened “I.H.C.”
With this information Union agents were able to confirm that a man named Cammack had purchased twelve thousand muskets and shipped them from New York to an unknown destination. However, the damage had already been done, as the muskets were beyond the Union’s grasp. To arrest Cammack at this point would serve no purpose, so the agents gave him rope.
Within a week he hanged himself. His next enciphered message, which of course was immediately deciphered, stated: “Say to Memminger [the Confederate Secretary of the Treasury] that Hilton will have the machines all finished and dies all cut ready for shipping by the first of January. The engraving of the plates is superb.” The message clearly implied that equipment for printing Confederate money was then in New York awaiting shipment to the Confederate government.
Hilton, the engraver, was quickly located and arrested, and the plates were seized along with several million dollars in printed Confederate money.
History sometimes smiles in her postscripts. The plates, as the message indicated, were indeed superb. Without good plates the Confederate Treasury had to resort to atrocious engravings. It became easy to tell counterfeit Confederate bills, which began turning up in the South, from the genuine currency because the real thing was a far cut below even the poorest bogus money in quality.
Only once has a head of state publicly announced, in effect, that he had a copy of a potential enemy’s diplomatic code book, and that man was an American President. The story started in the early days of World War I , when upon occupying Brussels the Germans found they had captured a powerful transmitter that was not in operating condition. They were told that a twenty-year-old student named Alexander Szek could repair it, and he was promptly given the job. When it was again on the air, the Germans used it to transmit espionage and diplomatic messages.
The furtive whisperings of the transmitter were, of course, picked up by British monitors, and some of the messages were partially broken. Their significance drew the attention of Admiral Sir Reginald Hall, the legendary director of naval intelligence, who turned his attention to the station. Intelligence agents, working through a Belgian agent, soon discovered that young Szek, who by now had become a trusted German code clerk, had been born in Croydon, just outside London, and quite possibly was anti-German. The Belgian agent approached Szek, gained his confidence, and, with the help of letters from Szek’s relatives in England, finally persuaded him to copy the diplomatic code book. Over a period of three months Szek copied the columns of figures, which were forwarded via the Belgian agent to London.
In January, 1917, German Foreign Minister Arthur Zimmermann sent an astonishing message to the German legation in Mexico. The message was transmitted through Count Johann von Bernstorff, the German ambassador in Washington, in 155 code groups of the “safe” diplomatic code. The German minister in Mexico was authorized, on behalf of the German government, to offer Mexico the three states of Texas, New Mexico, and Arizona if she would join Germany in a war against the United States. The British government, of course, decoded the message and disclosed its contents to President Wilson.
Here was a nice puzzle. If the contents of the note were made public, the Germans would know that their diplomatic code had fallen into the hands of England or the United States. On the other hand, the bold effrontery of the message cried for public disclosure. Wilson decided that a crystallized public opinion was of greater value than any further information that might be obtained by intercepting other messages in the German diplomatic code. He made public the German offer to Mexico. An effort was made to cover up the fact that the code had been stolen, and Szek was spirited out of Brussels. In a strange aftermath to one of the strangest stories to come out of the code rooms, the code thief disappeared from the ship that was bearing him to England and safety. Some speculate that a German agent was responsible for his disappearance. After the war Szek’s father accused the British of having engineered his son’s disappearance to prevent the Germans from learning how they lost their topsecret code.
But the most bizarre episode in the annals of American cryptography began when a fleet of zeppelins floated skyward for what was to be the last great raid on London in October, 1917. At that point not only was London suffering the terrors of the raids, but German U-boats had recently been enjoying their greatest successes on the high seas. There was some hope of relief from the submarines; the new convoy system was proving effective, and British divers had recently obtained from a sunken submarine a copy of the Imperial German Navy’s code book. But two vital types of information were missing from the book: the identifying call letters of the German U-boats and the enciphered letters that pinpointed, for German naval headquarters, the position of a submarine whenever it transmitted a message.
At this point a windstorm intervened for the Allies. The high winds blew straight against the noses of the zeppelins returning from the big raid. By morning four of the huge bags had used all their fuel and were drifting helplessly across France. Zeppelin L-49 gradually settled toward the ground, scraped the trees, bounced across the fields, and at last came to rest and was captured on a farm near Chaumont. By the hand of fate, Chaumont was the headquarters of the American Army.
Colonel Richard Williams of American intelligence at Chaumont started unravelling an interesting line of thought. Each zeppelin probably carried a code book. What could the commander do with the book when he found himself adrift across France, his fuel exhausted? He couldn’t drop it overboard, as he could over open seas. He couldn’t burn it—indeed not, beneath that vast hydrogen-filled bag. Williams decided that if he had been commander of the L-49, he would have torn the code book into fragments and scattered the pieces into the wind. And it might have been one of the last acts carried out aboard the stricken ship.
The enterprising Williams gathered a detail of men and retraced the bumping, scraping trail of the downed zeppelin. Within a quarter of a mile the men began finding scraps of paper. By nightfall they had gathered a whopping twenty-two gunnysacksful. They took their find to the huge map room and began working on the gigantic jigsaw puzzle.
They had little success. About midnight, when they were tempted to give up, Lieutenant Samuel Hubbard walked into the room. An amateur yachtsman, Hubbard had sailed the North Sea prior to the war. On one fragment of the maze of shredded paper, a fragment with a faintly bluish tinge, he thought he recognized a bay he once had known and suggested that the men sort out all the bluish pieces. Soon a huge chart began to take shape, a chart of all the North Sea waters sailed by German submarines. The chart was gridded with position lines, and each line was labelled with its cipher symbol. These were the symbols that had been lacking. As a bonus one of the men produced from his pocket a small book that he had picked up and intended to keep as a souvenir and asked if it was of any significance. The book contained a photograph of every vessel in the Imperial German Navy, along with its coded call sign.
Today it is difficult to evalute the results of Colonel Williams’work with pastepot and scraps of paper. In the single month of April, 1917, some 840,000 tons of Allied shipping had been sunk. By November those losses had been cut by two-thirds as a result of the convoy system hastily inaugurated in the intervening months. But cryptography buffs point out that during November, the month after the zeppelin code book had been strewn to the winds, nine U-boats were sunk, and the submarines were never again a menace.
After the sudden disbanding of Yardley’s group of cryptographers between the wars, no black chamber of any size existed in the United States until the approach of World War II . During that war a good many oss agents were given code and cipher training in the basement of the oss administrative building overlooking a Washington brewery. The trained eyes of the agents quickly spotted the brewery, and the trainees regularly followed the tourists on guided tours to collect the inevitable glass of free beer after arduous hours of memorizing cipher systems.
Despite the horseplay, the oss developed a code system that, for simplicity and effectiveness, was ideally suited to its needs. During an agent’s training, between glasses of free beer, he was required to memorize a numerical equivalent for each letter of the alphabet. No two agents learned the same “numerical alphabet.” Later, prior to each field mission, he was supplied a copy of what was called a one-time code pad; the only other copy was at his headquarters. The code pad was simply a sheet imprinted with rows of numbers selected at random by machine. The sequence of numbers was of no importance whatever to the system—only that the two pads were identical. When the agent wished to transmit a message, he did it letter by letter. If the first letter of the message was T and his memorized equivalent for T was 16, he added 16 to the first number on the code pad and transmitted the total. The recipient, of course, subtracted the first number on his code pad in deciphering the message. The system was virtually foolproof because no agents had the same numerical alphabet; each code pad was different, with numbers chosen at random; the odds were high that any one letter of the alphabet would have a different numerical value each time it appeared in the message; and even if the code pad was captured, it was useless to the enemy without the memorized numerical equivalents of the letters.
The system, for example, would be used to radio instructions for an airdrop of particular supplies in Burma. The enciphered message further stipulated a recognition code for the pilot of the supply plane. At the appointed hour and spot the agent would lay out recognition panels in a coded pattern. Upon seeing the panels displayed correctly, the pilot buzzed the spot the number of times designated in the message, then watched. The panels had to be rearranged in another coded pattern before he would make the airdrop.
Today the National Security Agency, the supersecret arm of the Department of Defense, is primarily responsible for the important code and cipher work of the United States. Its huge building, a few miles north of the nation’s capital, houses thousands of scientists, engineers, and mathematicians. It constantly seeks men trained in computer work. It seems obvious that computers have taken over at least some of the nation’s cryptography and cryptanalysis. They would appear to be ideally suited to such work. A highly secret message, for example, could be translated into digits by any normal ciphering system. These digits could then be fed into a computer with instructions for processing them. According to the instructions the computer could differentiate them a million or more times within a few seconds and produce a simple mathematical equation—the encoded message. Each differentiation would be the equivalent of reciphering the message into a completely different system. The receiving computer, operating on reverse instructions, would work backward from the equation, integrating as many times as necessary, and produce the numerical equivalent of the plaintext. The theoretical system described here is speculation but well within the abilities of existing computers.
It would appear virtually impossible to break such a computer system. Yet other ciphers and codes, seemingly impregnable in the past, have succumbed to the assaults of the men of the black chambers. If one computer can encode a message, another can break the code. Today, perhaps, computer is pitted against computer, but the secret war of the black chambers continues.