Chapter 15 Chapter Thirteen

Not long after I was assigned to investigate Mitchell, I learned about the greatest counterintelligence secret in the Western world—the "Venona" codebreaking method.To understand what "Venona" is and what it really means, you need to know a little about cryptography.In the 1930s, intelligence services, such as those of the Soviet Union and the United Kingdom, used the one-time pad communication system.This is the safest way, because only the sender and receiver have the codebook.Each codebook is only used once and destroyed immediately after use.This cipher cannot be deciphered at all.To send a message with a one-time code book, the sender must first translate each word into a four-digit number according to the code book.For example, if the first word of the telegram is "defense", then it may be translated as 3765.Then add the first set of numbers on the one-time pad, such as 1196; if the "Fibonacci" system is used, this number becomes 4851.This is actually a double passcode. (The "Fibonacci" system is also known as Chinese arithmetic. Its fundamental principle is that numbers larger than 9 do not carry, because the carry will cause regular distribution. Therefore, all cryptographic systems at that time adopted the "Fibonacci" system.)

In the early days of the war, due to the lack of cipher materials for the Soviets, we successfully developed the "Venona" cryptography method.In order to ease the pressure on the communication system, the Soviets made multiple copies of the one-time code book and distributed them to the Soviet embassies in Western countries.In this way, it will be difficult for us to decipher their codes.The Soviets used five channels to broadcast massive telegrams around the world—one for embassies; one for the GRU; one for Naval Military Intelligence; one for the KGB; and one for trade communications.During the war, many military equipment were transported from the West to the East, and trade communications accounted for 80% of the national communications of the Soviet Union.KGB operatives in Washington communicated with Moscow using a copy of a codebook used on the trade corridor between the Soviet embassy in Mexico and Moscow.

Shortly after the war, a brilliant American cryptanalyst named Meredith Gardner began studying a mutilated Soviet cipherbook he had picked up on a battlefield in Finland.Gardner worked for the U.S. Armed Forces Security Service, the precursor to the NSA.Although most of this codebook has been lost, it still contains some of the most common directive phrases in radio communications, such as "spelling", "spelling finished", and so on.These phrases are used very commonly because each codebook has its own defined vocabulary.If the sender does not find a suitable phrase in the cipher book - which is often the case, such as a person's name - he has to spell the word letter by letter, prefixing the word "Spelling", add "Spelling" at the end of the word to remind the other party's attention.

Gardner compared these commonly used phrases with the Soviets' telegram communications in the past, and found that some channels had the same code reused, which indicated that the Soviet Union was using the same one-time pad.One by one, he "matched" those communications encoded with the same codebook and tried to decipher them.At first no one believed him when he claimed he had broken the Soviet code.He later made a successful move against the ambassador line from Washington to Moscow.At this time, people began to pay attention to his contribution.The code he deciphered was an English sentence called "Defense cannot win victory!" This sentence is preceded by "Spelling" and followed by "Spelling is over".Gardner discovered that this sentence turned out to be the title of a book on national defense strategy published by the United States the day before the cable was sent.So the U.S. Armed Forces Security Agency told the secret to Britain, whose cryptanalysis work at that time was the best in the world.Since then, the United Kingdom and the United States have begun a joint operation to decipher the code, and this work has continued for forty years.

The code name for the operation was first "The Bride", then "Pharmaceuticals", and finally "Venona", and was only known in the UK as "Vinona".The action is moving very slowly.It takes a lot of time to find a signal that can be matched in the vast communication, and even if such a signal is found, it may not be possible to decipher the messages on both sides.The codebook Gardner picked up was incomplete, and the codebreakers could only use "indirect" intelligence.For example, they could use "indirect" intelligence to decipher trade communications if they found a match between the KGB channel between Washington and Moscow and the trade channel between New York and Moscow. "Indirect" intelligence was gathered on the basis of message dates in shipping bulletins, cargo records, ship arrival and departure times, tide schedules, etc.Based on this intelligence, cryptographers can guess the contents of trade communications.Deciphering either side of the matching signal provides the codebook with more phrases that can help decipher the message on the other side of the matching signal.

Britain and the United States jointly developed a key device for expanding the deciphering range of "Venona", called "window index".Whenever we deciphered a phrase or phrase, we made a note of the corresponding correspondence on this index.The British began to use more advanced means of indexing. They added two sets of undeciphered words on both sides of the deciphered word or phrase. After a period of time, the window index appeared to be repeated.This repetition allows deciphered phrases to bring out a set of undeciphered phrases and provides sufficient indirect intelligence for deciphering new phrases, and expands the scope of the window index.Another new technique used to break codes is the "drag" technique.If "spelling spelling is complete" or various nouns appear in the communication, and the cryptographer does not know which letters are missing in the spelled word, then input it into the electronic computer, and let the computer "drag" these words to other waveforms. The computer then outputs a list of repeated words, and the cryptanalyst analyzes and studies the repeated matching signals from the reverse side, so as to decipher the sequence of "spelling and merging".

This technology is not very perfect, and it often takes a month to decipher one or two phrases.Of course, sometimes there are cases where the progress is rapid. For example, the Americans found the full text of the recorded speech in the channel dedicated to the ambassador in Washington.The technology also often encounters some new and thorny problems: how to use one-time pads in unorthodox ways, or whether to fold up or down, and so on.These problems add considerable difficulty to the work of finding the matching signal.There is also a problem with code books, some of them have been modified, and the Ambassador, GRU, and Trade Waves use an alphabetical code book, much like a dictionary, so the cryptographers can only Guess the approximate position of the phrase in the codebook from the spelling of the phrase in the message.The codebook used by the KGB is a special multi-volume random arrangement codebook, which made the staff who matched the KGB channel code a headache. The work involved in "Venona" is very arduous. For several years, the British Government Communications Headquarters, the US National Security Agency and the British MI5 have employed a large number of researchers to collect "indirect" intelligence around the world. However, Of the 200,000 intercepted messages, we have deciphered less than one percent, and in many of them only a few words have been deciphered.

But judging from what we know about counterintelligence and the attitude of the secret world, the "Venona" operation has had a huge impact on the intelligence services of the United Kingdom and the United States.In the late forties we made great progress in deciphering the KGB's New York-Moscow and Washington-Moscow channels.From the deciphered telegrams, we can see that Soviet espionage in the United States was considerable throughout the war and postwar.There are more than 1,200 aliases in the telecommunications, and since these are often part of the "spelled spell end" sequence, they are the easiest to identify, although we cannot necessarily decipher them.We estimate that among the more than 1,200 aliases, more than 800 aliases were spies developed by the Soviet Union.They are low-level liaisons who make up the majority of the intelligence network.Some of them are also important, for example, there are fourteen spies working in or around the Office of Strategic Intelligence (the predecessor of the CIA), and another five spies can enter and exit the White House in different ways. According to deciphered cables, one of them was Fly back to the United States from Moscow on Ambassador Avril Harriman's private jet.However, the most threatening thing is that the Soviets planted a group of spies in the U.S. atomic weapons development unit, and another group of spies could even see every important document of the British and American governments in 1945, including the documents given by Churchill. Telegrams from President Roosevelt and later President Truman.

Clues obtained by deciphering codes have solved many cases.It has now been found that McClain was one of the spies who read Churchill's telegram, and Klaus Fuchs and the Rosenbergs were part of the nuclear spies.We compared the geographical clues for deciphering the codebook with the long-term operations of Alger Hiss, a senior official of the US State Department, and found that he was probably the spy who flew on Harriman's plane.But our best efforts at counterintelligence and code-breaking failed to catch most of the aliases. Things are just as bad in the UK.There is only one difference, that is, the United States has been tracking radio communications between the Soviet Union and the United States during and after the war, while Churchill in the United Kingdom ordered the cessation of all anti-Soviet intelligence work during the wartime alliance, and the Government Communications Headquarters also went to the wartime. Only after re-tracking the Soviet communications.Therefore, the British received very little communication, and only once deciphered it, that is, from September 15th to 22nd, September 1945, the KGB Moscow-London channel was deciphered for a week Work.

Among the correspondence we found some cables addressed to Boris Krotov, a KGB officer at the Soviet embassy in London.Krotov is specifically in charge of commanding high-level spies.These cables came at a time when Soviet intelligence agencies in the West were going through a crisis of sorts.Igor Guzenko, a young GRU cryptographer at the Soviet embassy in Canada, had just defected to Western countries with a large amount of information, and exposed to Canada and the United States the spies planted by the Soviet Union in these two countries.Guzenko also exposed a nuclear spy named Alan Nunn May to the UK.Most of the cables sent to Krotov from the Moscow Center were orders telling him how to deal with his subordinates.A total of eight aliases were mentioned in the cables, three for the spy network formed by Stanley, Hicks and Johnson, two for inseparable friends David and Rosa, and three more.During the weekend, all communication between Moscow and these eight spies was interrupted, and in the future, we will use face-to-face contact. Except for special circumstances, the communication will be carried out once a month.

When I first came into contact with "Venona", I was fortunate enough to see the communication records of the KGB channel from Moscow to London reproduced by the Communications Headquarters.Every time the Communications Headquarters deciphered several new ciphers in the telegram, it copied the telegram and stamped the words "Top Secret Photocopy Venona" on the copy, indicating the sender and recipient, the sender and the recipient. Items such as date and time, channel and bearing (e.g. KGB Moscow, London), message class (normal or urgent) were distributed to a small number of senior officials for review.Here is a similar message: (It's a cable that hasn't been fully deciphered, and a challenge for us.) The secret offered by "Venona" is terrible because it is so incomplete.The deciphered telegram clearly told us that these eight aliases were all important spies, and the Soviets took protective measures against these eight spies and Krotov in September 1945, because the Soviets knew that we had discovered Krotov is directing the spies.But the telegrams did not help us identify the spies.The Communications Headquarters only sent the translations of the telegrams that had been checked by them, including the telegrams that were not fully deciphered.When they sent the translations, they often attached a page of draft translations with guesses about strange phrases in the telegrams, which could not be checked.As the number of phrases deciphered continues to increase, the message needs to be reissued. Therefore, a message is often repeated several times. Stanley, we're sure he's Philby.Golitsin had heard of the code name Stanley.Golitsin said Philby had something to do with KGB operations in the Middle East, but we couldn't find evidence in the cables.Hicks was almost certainly Burgess, and there was not only a reference to the spy network in the cable, but also a vague reference to Hicks' temper.Johnson was presumably Brent, but there was no evidence of that either in the cable.The other five spies remain a mystery.We can rule out McClain because he was in Washington in September 1945.Obviously these findings are of great help to our investigation of Mitchell.Any of the five aliases could be hiding in MI5.I read the deciphered part of the telegram over and over again, feeling very anxious and unable to do anything.I remember wondering how the senior executives of MI5 fell asleep every night for more than ten years after we deciphered the telegrams. The strangest thing is that in 1954 "Venona" stopped on both sides of the Atlantic.Cryptanalysis work was initially developed in the late 1940s and early 1950s. Due to various twists and turns, the subsequent progress was slow, and now it is almost at a standstill.Artificial "fitting" has reached the limit of human thinking ability.At that time, electronic computers were not capable enough to push "Venona" to a new level of development. Another reason Venona stalled: In 1948 the Soviets made changes to the cipher programs they were using around the world and canceled all copied ciphers.Australia's last Operation Venona suffered losses due to these changes.Prior to this, Australia's "Venona" operation was so successful that even the British and Americans had to rely on their operations to collect Soviet messages.The Australians didn't know that Britain and the United States were engaged in the "Venona" operation at the time, and the British told them only afterwards.Only when the infiltration of Soviet spies continued to expand, especially when it affected the Foreign Office, did we report the information obtained to the Australian Government in summary form.Soon, with the help of MI5, Australia finally established its own intelligence organization - the Australian Security Intelligence Organization. We didn't know why the USSR changed the codes until the early fifties.It turned out that the deciphering of the Soviet code leaked the wind, and the leaker was William Weisband, a young employee of the Security Bureau of the US Armed Forces.Wesband didn't actually know the Soviets' losses until 1949, when Philby joined the effort.Hollis was involved in this work in 1948.He later went to Australia to help them set up the Australian Security Intelligence Organization.As soon as he returned to China, the "coincidence" in Australia stopped. Although the Soviets could cancel the copied one-time pad, they could not prevent us from studying their telegrams before 1948.In 1949 Philby was relocated to Washington, which allowed the Soviets to monitor the progress of our deciphering efforts.The Soviets knew that after the "Venona" leak, sooner or later we had to solve various technical difficulties in finding more "coincident" signals.In 1954, "Venona" basically stopped. A few years later, I arranged for Meredith Gardner to visit the UK and asked him to help us continue the Venona operation in the UK.Gardner was a quiet bookworm who had no idea that other cryptanalysts were afraid of him.He used to tell me how he did "stitching" in his office, and told me about a young pipe-smoking Englishman named Philby who used to visit him at work and stole from over his shoulder. Look at his work and give him a big compliment.In the late sixties, Gardner became disillusioned and annoyed by his sensitivity to the fact that we were using his codebreaks for things other than mathematics. "I never wanted it to get anyone in trouble," he often said.After he found out that his success pushed some people into the elevator, he was shocked.He agreed with me that the Rosenbergs deserved leniency despite their serious crimes.In Gardner's eyes, "Vinona" is a work of art that should not be tarnished by brutal McCarthyism.But a few officials in the intelligence services of the United Kingdom and the United States regarded the success of breaking the code as a major victory in the Cold War.This view underpins counterintelligence investigations, and that intensification has permeated Western intelligence for decades after we first broke the Soviet codes.Because although Western political leaders sincerely extend a hand of friendship to the Soviet Union, the Soviet Union conducts espionage on a large scale all over the world.For example, during that week in September, the Moscow KGB channel sent a large number of telegrams to the United Kingdom, detailing how to escort allied prisoners of war to the Soviet Union, because these prisoners of war had opposed the Soviet Union, such as the Cossacks.Many of the cables were arrest warrants and lists of those to be arrested immediately.By the time I read these cables, the people mentioned were already dead, but the other intelligence officers must have been shocked: the peace of 1945 was not really achieved, it was just a German concentration camp turned into a Soviet Gula That's all. In 1959, the "Venona" operation was revived again.GCHQ discovered that the Swedish Signals Intelligence Service had intercepted and stored a large number of wartime communications, including messages between the Soviet GRU and London in the early days of the war.GCHQ persuaded the Swedes to abandon their neutrality and send the material to Britain for study.We found out that there was a material in Sweden code-named "Buckle", so we transferred Arthur back to the D Division.Arthur was one of MI5's officers with direct experience with Venona, who had worked on Venona during the investigation of the Fuchs and McClain cases. We have placed great expectations on the "buckle" material, trying to obtain more information through this material, and broke the pseudonym that has not yet been found out.We want to use this to promote the progress of the "Venona" operation.In addition, this material can also provide more phrases for the codebook, expanding the scope of our deciphering of the existing "Venona" telegrams.Since the advent of powerful new electronic computers, restoring the whole operation has become even more meaningful (in the 1950s I did not believe our efforts would be in vain).Thanks to Arthur's strong support, the pace of our "Venona" operation continued to accelerate in the early 1960s. In fact, the British intelligence part of the "buckle" material is not important.Much of this information consisted of reports by Soviet GRU officials of air raid damage across Britain and estimates of British military strength.There are dozens of pseudonyms in the material, some of which are meaningful, but these people have long since died.For example, there is a spy named Haldane who has studied deep diving technology at the Hasla Submarine Test Station of the Admiralty.His task was to provide details of various research programs to the Soviet GRU staff in London through the British Communist Party.From the telegram we also got information about another spy named Owen Montagu.Owen, the son of Lord Swaythling (not to be confused with Euan Montagu, who was another man who had organized the famous wartime Operation Extraordinary), was a freelance journalist.From the telegrams, we can clearly see that he collected political intelligence inside the Labor Party for the Soviets, and also collected some intelligence inside the British Communist Party. We took a special action against the GRU telegrams of the Soviet Union by comparing their telegrams with those of the KGB four years later.We found that the GRU officials in 1940 and 1941 were less capable. After Stalin's purge in the 1930s, they fell into a slump and looked for backers everywhere, flying around like a swarm of headless chickens.In 1945, the GRU replaced a group of new professional intelligence officers like Krotov. The overall spy management level was significantly improved, and they were very pragmatic.In addition, they also took careful protection measures for their spies, so that they could be used in the long run.At the time, the GRU's actions were lax, and according to the 1945 telegram, everything about them was controlled by the Moscow Center.We compared the channels used by the KGB with those used by David, and it became clear that the KGB held a very important position in the Soviet Union.In a sense, this is the legacy of the "Venona" deciphering operation-it made us recognize the giant machine of the KGB, whose intelligence network spreads all over the West, when the West is running around for peace At the same time, they were actively preparing for the Cold War. The "Venona" materials are kept in a specially secured office on the sixth floor.After I read the material there, I moved out and shared an office with Evelyn McBarnett.She is a researcher under Arthur and is busy investigating the Mitchell case.The Mitchell investigation was a bit of an odd time for D Branch.Hollis reassigned Furnival Jones from his previous position as chief of C, and Mitchell promoted him to deputy chief once he retired.Jones was replaced by Malcolm Cumming. The wise men in D, who were trying to follow the lead of the Lonsdale case, were not impressed by the appointment.And Arthur himself coveted the post of Director.On the basis of his achievements, Arthur could have been the director, but because of the positions he had taken in the early 1950s, he had not been appreciated by his superiors.They believed that Arthur was aggressive, short-tempered, and intolerant of others.Unfortunately, none of these were prerequisites for his success at MI5.After the Mitchell investigation was approved, Hollis decided not to tell Cumming about the investigation into Mitchell because Cumming was theoretically also a suspect.Leading the investigation was Jones, who oversaw the process from Branch C's headquarters on Kirk Street. Evelyn McBarnett was a strange woman with a large birthmark on her face.She is like a potted flower in the conservatory. She has been confined in the busy affairs of the office since she started working, and she doesn't know anything about the outside world. As soon as I moved into her office, she asked me, "Are you a Freemason?" "No, I don't approve of Freemasonry," I said. She said to me coldly, "I don't think you're going to be a Freemason, but if you want to succeed here, you'd better be a Freemason." Evelyn always thought there were spies inside MI5.She's a research officer and has been in counterintelligence for years, longer than Arthur and I.She can be said to be a living dictionary about office life, she has a flexible mind, and she is also good at judging people's characters, although sometimes she is a bit too much. "I'd guessed that sooner or later there would be an investigation," she told me. But she was pessimistic.She is convinced that the worst is yet to come, because investigation procedures are always pre-established. "If Arthur is too serious, he won't last long; and if you get involved with him, you have to be careful," she added. I was really taken aback. "Evelyn, what do you mean?" I asked immediately. She opened her safe and took out a black notebook. "Look at this!" she told me. Opening the notebook, lines of delicate and clean fonts came into my eyes, and I flipped through them quickly.It turned out that this notebook recorded the details of various cases in the 1940s and 1950s.Some of these cases I only know roughly, and some I don't know at all.The material was gathered from MI5 archives, and each case was an allegation of MI5 or MI6 infiltration. I was literally petrified, "Whose is this?" I asked. "It belonged to my friend Anne Last. She worked with me. She had collected them since the defection of Burgess and McLean. Then she resigned to marry. She married Charles Elwell. Before she left, she gave me this book, saying that it might be useful in the future." "Does Arthur know? . . . " "certainly." "Who else have you seen?" "Do I have to be chopped up..." I continued looking at my notebook.The name of Maxwell Knight is frequently mentioned in the opening pages.During the war, he believed that there must be spies inside MI5, and made records, but did not act.There are dozens of accusations in the record book, most of which are unrealistic imaginations.For example, based on a spy's report or casual thoughts and comments, there are also more specific materials, such as the testimony of Igor Guzenko.Guzenko was the young Soviet cryptographer who defected to Canada in 1945.His defection had a very big impact on the KGB communication of the British "Venona" project.For a week, the communication was in disarray.According to Anne Last, Guzenko had revealed that there was a spy in MI5 with the code name "Eri".When Guzenko was working in Moscow in 1942, he heard about "Eri" from a friend named Rubimov. At that time, it was Rubimov who handled the "Eri" telegram. "Eri" had some Russian background, he had access to certain files.The Soviet Union communicated with him by way of dead letter delivery, and often sent the information he provided to Stalin.This allegation by Guzenko was included in the archives along with his other materials, and no one cares about them anymore, and the materials had to be shelved and left there to eat ashes.It's incredible. Evelyn said: "People don't believe him, they think he's got it wrong, there can't be spies inside MI5..." The last page of the notebook is the author's "testament", she wrote: "If there is a spy in MI5, then I must be Roger Hollis or Graham Mitchell." I took a deep breath and said, "How can such a big person investigate? It can only be done completely if MI5 is turned upside down." "That's what they said in 1951," Evelyn said bitterly. Anne Last's notebook was nothing more than the first secret Evelyn and I shared.Over the next few weeks of working together, she gradually revealed to me a lot of MI5's forgotten history that we didn't hear on the A-2 tapes.These stories are full of questions, speculation, unexplained actions and bizarre coincidences.I soon learned that I was not the first to suspect that MI5 had spies.This fear has been around as long as the office furniture. In the evening, I walked through the bustling crowd towards Park Lane, Evelyn's story haunting my mind.Since 1942 there had been reports of spies within the military, but they had never been investigated and no one had refuted the reports.Time has dragged on too long, and the search must have been long and arduous.Thinking of this, I stopped and looked back at the Leconfield Building. "There won't be any leaks this time, right?" I thought to myself, "There won't be another defection, this person won't slip away..."