The Classified Code-Breakers of World War II
This article is a transcript of Campfire Stories: Astonishing History podcast Episode 8 (Part 2). You can listen to it on Buzzsprout, or wherever you get your podcasts.
Come gather around the campfire and let me tell you a story! Today we’re going to be talking about the code-breakers and code-talkers of World War II. This episode actually turned out longer than I thought, so I’m going to be splitting it into two parts. Part 1 discussed Native American code-talkers, including the Navajo and Comanche, and a special side story about the last Crow war chief Joe Medicine Crow. Part 2 will discuss Allied code-cracking teams including the stories of Alan Turing, Marian Rejewski, Elizabeth Friedman, and the Venona project.
Background of Cryptanalysis
Cryptography is the art of protecting information using codes and ciphers, and it has been used for thousands of years. In ancient times all the way until about World War I, it has been done on paper or with very simple machines, and then became more and more complex with the advance of technology. Modern codes are generally done with computers in a way that no human mind could break without technology. The Zimmeran telegram led to the U.S. entering World War I. Allies cracking Nazi codes may have shorted World War II by as much as two years.
The earliest codes seem to be from Ancient Egypt, where special hieroglyphs were carved into the tomb of Khnumhotep II to add hidden meaning to the legitimate messages written around 1900 BC. From 1500 BC, tablets from Mesopotamia were found with a code to hide a secret recipe for pottery glaze.
Simple Hebrew ciphers such as the famous Atbash cipher have been in use since about 600 B.C. Ancient Greeks used ciphers as well. The Spartans used a device known as a scytale, where a long strip of paper can only be read if it’s wrapped around a rod of a very specific diameter. The Romans continued their long-standing tradition of copying stuff from the Greeks when Julius Caesar used a cipher called the Polybius Square, invented by Greek historian Polybius.
Arab scholar Al-Khalil wrote the Book of Cryptographic Messages in the 700s and inspired the work of mathematician Al-Kindi about a hundred years later, who made arguably the greatest strides in code-cracking until World War II in his book: Manuscript for the Deciphering Cryptographic Messages. For codes where some kind of symbol or other letter or number replace the letters of the message, they are vulnerable to frequency analysis. Al-Kindi describes how you can examine the letters that are used most often in Arabic, or English, or whatever language you’re working in, and then see which symbols are used most frequently in the code.
During medieval times in England from about 800–1100, simple ciphers were written into manuscripts for fun. Leon Battista Alberti, an Italian renaissance man, became known as the “father of Western cryptography” for his writings on the subject. Codes blew up in Italy during the Renaissance, especially with the Vatican. Codes helped take down Mary, Queen of Scot’s plot against Queen Elizabeth I. Monarchs like King Louis XIV had chief cryptographers as part of their advisors. It remained most popular in Europe after the Islamic empires collapsed.
Throughout the 1800s, different historical figures worked on cryptanalysis, including Edgar Allan Poe, and Charles Babbage, the inventor of the mechanical computer.
World War I was when code-cracking started to get serious. Room 40 was a special cryptanalysis team in Britain who cracked over 15,000 German code using their analysis skills and German code books that had been recovered by Russian forces from a shipwreck.
Room 40’s most famous achievement was decrypting the Zimmermann Telegram. This was a message from the German Foreign Office to their ambassador in Mexico. It had dark proposal inside, that Germany was planning on attacking the United States, and that Mexico should join them and help them convince Japan.
This telegram being revealed is credited with convincing the United States to enter the war. The British officials turned the message over to U.S. President Woodrow Wilson and the U.S. declared war on Germany in 1917. The next year, the war was over.
Also during World War I, American engineer Gilbert Vernam created technology that would lead to the only type of truly unbreakable cipher, the one-time pad.
World War II
In World War II, traditional paper codes were used at the same time machine-made codes were really hitting their stride. Some of these code developments have only hit public knowledge in the 1990s and early 2000s.
Elizebeth Friedman
Elizebeth Friedman, Elizebeth spelled with three ees instead of an a, has been often called “America’s first female crytanalyst”. She was born to a Quaker family on a farm in Huntington, Indiana. She was the youngest of ten children, and graduated from Hillsdale College in Michigan with a degree in English literature, and experience in Latin, Greek, and German in 1915. She served as a substitute principal for a high school for several months and then moved back in with her parents. In 1916, she visited Newberry Library in Chicago looking for work, and spoke to the librarian.
The librarian ended up calling Colonel George Fabyan, the owner of Riverbank Laboratories, and told him about Friedman’s love of Shakespeare, which Fabyan was also interested in. In an incredibly dramatic move, Colonel Fabyan arrived in limousine and picked up Friedman to discuss a job opportunity. The project in question was to work with Elizabeth Wells Gallup and her sister from Boston in cracking hidden messages in Shakespeare plays to prove that they were truly written by Sir Francis Bacon.
Riverbank Laboratory became the only place in the U.S. capable of code-cracking before World War I. The U.S. government sent multiple people there to be trained with the fifteen staff members of Riverbank. One of the other employees was William Friedman, who as you might have guessed, was Elizebeths future husband. The U.S. War Department tried to recruit the Friedmans multiple times, but Colonel Fabyan stole their mail.
In 1921, the message finally got by him, and the Friedmans moved to Washington where Elizebeth cracked tens of thousands of codes involving Prohibition and international drug smuggling with the Navy, Coast Guard, Department of Justice, Treasury, Bureau of Narcotics, and Customs. She testified in court against smugglers and opium dealers, and trained dozens of other cryptanalysts.
She also helped settle a dispute between the U.S. and Canada over the ownership of a boat called “I’m Alone”. The U.S. Coast Guard sank the ship when it failed to comply with a search signal, and Canada sued the U.S. for damage, but Friedman helped prove the ship did not belong to Canada.
During World War II, Friedman and her team were the major source of information for Operation Bolivar, investigating the German spying network in South America, where it was feared Germany could be planning an attack on the U.S. from the south. During World War II Friedman’s team cracked 4,000 messages.
After Friedman and her husband retired, they wrote a book together called, “The Shakespearean Ciphers Examined”, which won multiple awards, going back to Elizabeth’s roots of how she started cryptology in the first place. After William passed away in 1969, Elizabeth worked on collecting his work, which has been described as the “most extensive private collection of cryptographic material in the world”, which is now housed at the George C. Marshall Research Library in Lexington, Virginia.
The couple had two children, Barbara and John, and Elizabeth passed away in 1980, at the age of 88. In 1999, she was inducted into the NSA Hall of Honor, in 2002, an NSA building was jointly named for the Friedmans, in 2019, there was a Senate resolution passed a resolution honoring her, and in 2020 the U.S. Coast Guard announced they’re naming a ship after her.
Uncle Sam’s Code-Breakers
In the United States, the code-breaking team ran through the Army was the Signal Intelligence Service, known as SIS, which would one day morph into the National Security Agency. Originally founded in 1930, it took over the Arlington Hall Junior College for Women when the war began, in Arlington, VA near D.C. SIS was part of the Signal Corps department of the Army.
SIS trained soldiers for work in the field and also provided secure equipment. The agency was started with three former math teachers named Frank Rowlett, Abraham Sinkov, and Solomon Kullback, and one army cryptographer trained at Riverbank lab before World War I. By the end of World War II, there were 10,500 staff members, 7,000 of whom were women.
Anne Caracristi, who later became the Deputy Director of the NSA, worked there in a mainly female unit who helped to sink two-thirds of Japanese ships. During the war, SIS had stations in Virginia, California, Hawaii, Alaska, India, and Eritrea.
The Allies Link Up
The United States code-breaking team, the Signal Intelligence Service broke the highest level Japanese code system, nicknamed Purple, before World War II even started. Purple had replaced another Japanese machine called M-1 Orange, which was broken by U.S. Navy code-cracker Agnes Driscoll, who also went by the fantastic nickname Madame X. The U.S. won the Battle of Midway at least partially because they had cracked Japanese code system JN-25, which the Japanese did not notice and continued using.
The American intelligence team called information from their code-cracking “Magic” while the British called it “Ultra”.
There have been another thing that contributed to the Allied success at code-breaking. There were 7,000 women working at the British Station X, and 11,000 working near Washington, D.C. The Japanese and German employed next to none.
The success of American code-breakers Agnes Driscoll and Elizabeth Friedman directly before the war led the U.S. Army and Navy to actively recruit top female college graduates in the late 1930s and early 1940s.
The Americans and the British militaries used similar machines to Enigma, but they were never cracked by the Axis. The British field agents used the extraordinarily British strategy of poem ciphers, where they would memorize poems to be used as the key to the message, but later switched to one-time pads.
In 1943, SIS began working on the Venona project, intercepting the coded messages of America’s ally at the time, the Soviet Union. By the end of the war, they had gathered 200,000 Soviet messages. After the war, American codebreaker Meredith Gardner, discovered evidence of Soviet spying at Los Alamos National Laboratory, the location of the radioactive accidents covered in Episode 1 of this podcast. However, because it could not be revealed that the U.S. was spying on the Soviet Union at all, the U.S. government couldn’t use the cracked messages from the Venona project when they charged the spies.
Venona and the Rosenbergs
The U.S. ran the Venona Project during World War II and continued through the Cold War into 1980 to decrypt Soviet communications. The project decrypted about 3,000 messages. They discovered the Cambridge 5 espionage ring that operated in the U.K. from the 1930s to the 1950s, and also Soviet spying on the Manhattan Project, the building of the nuclear bomb, which is discussed in Episode 1 of this podcast. The Soviets were using one-time pads, which as mentioned, when used correctly are uncrackable. The problem was that the Soviets accidentally reused entire pages of code in multiple one-time pad booklets, which allowed them to be cracked by American cryptanalysts. Most of these codes-crackers were young women.
Perhaps the most well-known case that the Venona project contributed to was the arrest and execution of spies Julius and Ethel Rosenberg. The Rosenburg’s were a married American couple who passed nuclear weapons designs and designs for other equipment like sonar to the Soviet Union and caught in 1951. The couple were both raised in New York City and met as members of the Young Communist League.
Julius worked for the U.S. Army as an engineer from 1940–1945 until his connections to the communist party were noticed. The Rosenbergs recruited multiple other Americans to act as foreign agents, and passed along thousands of pages of documents. By 1949, the Soviet Union was able to do their first nuclear test, code-named “Joe-1” by the U.S. in reference to Joseph Stalin.
When sentencing the Rosenburgs, Judge Kaufman said,
“I consider your crime worse than murder … I believe your conduct in putting into the hands of the Russians the A-bomb years before our best scientists predicted Russia would perfect the bomb has already caused, in my opinion, the Communist aggression in Korea, with the resultant casualties exceeding 50,000 and who knows but that millions more of innocent people may pay the price of your treason. Indeed, by your betrayal, you undoubtedly have altered the course of history to the disadvantage of our country. No one can say that we do not live in a constant state of tension. We have evidence of your treachery all around us every day for the civilian defense activities throughout the nation are aimed at preparing us for an atom bomb attack.”
Safe to say, public opinion against the Rosenbergs was swift. There were campaigns to save the Rosenbergs, particularly Ethel, claiming that they were innocent, sentenced too harshly, or were victims of anti-semitism. No major Jewish organization in the U.S. took up their cause, and the ACLU declined to get involved. Although many prominent figures in the U.S. and abroad asked for them to be pardoned, including Albert Einstein, Jean-Paul Sartre, Frida Khalo, Diego Rivera, and Pope Pius the 7th, the Rosenbergs were sent to Sing Sing prison in New York, and were executed by electric chair in 1953.
It was originally scheduled for 11 p.m. on June 18th, which was during the Jewish sabbath, which their lawyer protested. In response, the judge moved it up to 8 p.m., which I can’t imagine is what their legal team was going for. They were the only civilians executed for espionage in America during the Cold War. Their two children, Michael and Robert Meeropol, were adopted by Abel Meeropol, the writer of the song “Strange Fruit” and another member of the American communist Party, and Michael and Robert have campaigned for exoneration for their parents for decades.
Enigma
Now let’s talk about the mama of all code machines. Before World War II even began, the Germans developed a type of encryption machine called the Enigma. To the untrained eye, which is mine, the Enigma machines look like a complicated typewriter. A person could put their little Nazi fingers on the keys and type a message, and several rotors inside would switch the letter with another letter multiple times and then output the coded message made up of scrambled letters.
By using multiple rotors inside the machine, an Enigma with three rotors could produce 17,000 letter combinations before it repeated itself. To add an extra level of security, a plugboard device sat in the middle of the machine and swapped pairs of letters every so often. When the message was typed, the coded letter would light up on the keys and the person sending the message would write it down and send the lit letters through Morse code. Then the receiver received gibberish in Morse code and used another Enigma machine set up the same way to decode it.
That’s about as much technical description you’re going to get from your host the international studies major who dropped out of STEM immediately after entering college, but there’s a lot more information online if any math or engineering nerds out there want to check that out.
Now lets talk about Polish college students Marian Rejewski, Henryk Zygalski, and Jerzy Rozycki. The three men had been regular mathematics students at Poznan University when they were recruited for a secret cryptology course hosted off-campus at a military facility.
They continued their regular courses while taking these secret classes at night. They joined the Polish Cipher Bureau officially in 1932. By the time they got there, one version of the Enigma had already been cracked, but the new version with the plug board added hadn’t been figured out yet. Rejewski worked on it in secret, alone, for several hours a day, not allowed to tell even his other colleagues.
To break the new Enigma, Rejewski needed to know how the machine generally worked, how the rotors inside were wired, and the set-up that was changed by the Germans every single day. The Polish Cipher Bureau already figured out the way it generally worked. The French military captain Gustave Bertrand and one of his spies, Hans-Thilo Schmidt captured German manuals and supporting documents. Rejewski used these documents and his math background to determine the design of the Enigma machine in 1932. This allowed Rejewski, Rozycki, and Zygalski to build their own Enigma machines as a copy, called the Enigma doubles. By 1933, they could start cracking German messages.
But in 1938, the Germans made their devices more complicated, and the Polish team didn’t have the resources to match it. So in 1939, the Polish teams decided to let the French and British in on their Enigma decrypting system. In September of that year, Poland was invaded by the Nazis. The British military completed Mission 4, where they evacuated Marian Rejewski, and three other code-crackers, Gwido Langer, Jerzy Reozycki, and Henryk Zygalski.
The British team took their Polish charges into the neutral country of Romania and then into France, where the Polish team continued working with British agents to break the newest changes to Enigma. The British team workers out of an English countryside mansion-turned code breaking station known as Station X. These British code crackers included British-American mathematician Gordon Welchman, and British mathematicians Max Newman and Alan Turing.
The British were able to use this knowledge in their Ultra project.
A head of the project said that the Enigma code-cracking “would never have gotten off the ground if we had not learned from the Poles, in the nick of time, the details both of the German military version of the commercial Enigma machine and of the operating procedures that were in use.”
After the Enigma was broken, the Germans developed Schlusselgerat 41 to replace it, but it wasn’t widely used. When the war ended, the British intelligence officers were told not to reveal that the Enigma had been broken, as they were worried the defeated Nazis would say that they had been beaten unfairly.
Alan Turing
Alan Turing is one of the most famous code-crackers to ever live. He was born in London in 1912, and his middle name literally had the word Math in it, Mathison. His father was on leave from the Indian Civil Service, and his mother was from an English-Irish noble family. He had one older brother, John, and his parents would often travel to India for his father’s work, so the children would stay with family friends.
He was enrolled in school at age 6. When he was 13, Turing was sent to boarding school, and when a strike shut down transportation, he rode his bicycle for 60 miles to make it there for the first day. Although Turing’s STEM skills were recognized early, his teachers at Sherborne Academy were not pleased, as they focused more on classics. The headmaster wrote to his parents:
“I hope he will not fall between two stools. If he is to stay at public school, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a public school.”
By 16, he was solving complex math equations and deducing Einstein’s laws.
While studying at Sherborne academy, he met Chrisopher Morcom and the two fell in love, obviously not accepted at all at the time, but Morcom died in 1930 after developing bovine tuberculosis, which he got from drinking milk from an infected cow. Turing was devastated, writing a letter to Morcom’s mother that said:
“I am sure I could not have found anywhere another companion so brilliant and yet so charming and unconceived. I regarded my interest in my work, and in such things as astronomy (to which he introduced me) as something to be shared with him and I think he felt a little the same about me … I know I must put as much energy if not as much interest into my work as if he were alive, because that is what he would like me to do.”
Turing continued to write her for many years. Although Turing has been known as an atheist, he wrote to Marcom’s mother at one point,
“Personally, I believe that spirit is really eternally connected with matter but certainly not by the same kind of body … as regards the actual connection between spirit and body I consider that the body can hold on to a ‘spirit’, whilst the body is alive and awake the two are firmly connected. When the body is asleep I cannot guess what happens but when the body dies, the ‘mechanism’ of the body, holding the spirit is gone and the spirit finds a new body sooner or later, perhaps immediately.”
Turing studied at King’s College and became a fellow, publishing multiple papers and proving multiple mathematical laws that I don’t have enough background in to begin to understand. He received a PhD in 1938 in mathematics and created the Turing machine.
The day after the UK declared war on Germany, Turing went to Bletchley Park Station X to work on codebreaking. Turing and Dilly Knox, a colleague built off of the Polish work on the Enigma machine. He published two papers about mathematical approaches to cryptography that were kept classified for almost seventy years because of their broad valuable addition to the field.
At Station X, Turing was known for being slightly eccentric, known by the nickname “Prof”. A colleague wrote of him,
“In the first week of June each year he would get a bad attack of hay fever, and he would cycle to the office wearing a service gas mask to keep the pollen off. His bicycle had a fault: the chain would come off at regular intervals. Instead of having it mended he would count the number of times the pedals went round and would get off the bicycle in time to adjust the chain by hand. Another of his eccentricities is that he chained his mug to the radiator pipes to prevent it being stolen.”
Another said,
“It is a rare experience to meet an authentic genius….However, the experience of sharing the intellectual life of a genius is entirely different; one realizes that one is in the presence of an intelligence, a sensibility of such profundity and originality that one is filled with wonder and excitement. Alan Turing was such a genius, and those, like myself, who had the astonishing and unexpected opportunity, created by the strange exigencies of the Second World War, to be able to count Turing as colleague and friend will never forget that experience, nor can we ever lose its immense benefit to us.”
Turing was also a long-distance runner who sometimes ran 40 miles to London for meetings. He tried out for the 1948 Olympic team, but was injured. Despite his injury, he was only 11 minutes slower than the silver medalist final time for the Olympics.
Turing developed a device called the bombe to break the Enigma codes. Several of them were developed and used by the Station X team to break the codes. They wrote to Winston Churchill asking for additional resources, and the letter was described as having a “electric effect”. Churchill wrote a memo in response to a general,
“ACTION THIS DAY. Make sure they have all they want on extreme priority and report to me that this has been done.”
Two hundred bombe devices were eventually made.
Turing went to the United States in 1942 to work with the U.S. Navy. He also developed a system for encoding electronic speech over the telephone. He and his colleague, engineer Donald Bayley, developed a device called Delilah, although it was made too late to be widely used in the war.
After the war, Turing produced a paper with a design for a stored-program computer, called the ACE, and while he was on sabbatical, the first ACE machine was built without him. He continued working on early computers at the Computing Machine Laboratory and continued working on computer programs and mathematical papers. He also proposed the idea of the Turing test, which is still discussed as a way to tell if a machine is truly “intelligent” in a way indistinguishable from a human by a third party. The CAPTCHA test is considered the reverse of a Turing test.
Turing also suggested that instead of trying to build a computer program that was as intelligent as a adult, the goal should be to make a child-like computer that could be educated. Turing also worked with a colleague to make a chess-playing program for a computer.
In the 1950s, Turing worked on mathematical biology, a field that uses statistics and calculus to study evolution and other biological processes.
Although Turing was a genius whose name would live on in infamy, his personal life was a dark one. Turing proposed to another cryptanalyst Joan Clarke, in 1941, but he eventually admitted that to her that he was gay. Although she was “unfazed” by this, Turing decided to break off the marriage.
About ten years later, when Turing was 39, he met a 19-year-old man named Arnold Murray outside of a movie theater and asked him out. A month later, someone broke into Turing’s house. During the police investigation, Turing admitted his relationship with Murray and both men were charged with “gross indecency”.
Turing eventually pled guilty and was given probation which included a so-called treatment. He was given hormonal shots of synthetic estrogen. His security clearance was revoked and he was removed from his cryptanalysis job. He was also blocked from entering the United States. He suffered this without being able to discuss the heroic work that he did during the war, as it was still classified and would be throughout the rest of his life.
On June 8th, 1954, Turing was found dead in his home at age 41. His housekeeper discovered him and it was determined that he had died of cyanide poisoning.
There are theories that Turing poisoned himself with a cyanide-laced apple, as a half-eaten fruit was found next to his bed. Snow White and the Seven Dwarfs was reportedly Turing’s favorite fairy tale.
However, professor Jack Copeland has proposed that Turing’s poisoning may have been accidental. Turing had a machine set up in his small room that used potassium cyanide to plate gold onto spoons. Turing regularly ate apples before bed, and despite what had happened to him, he showed no signs of depression. His hormone treatment had ended a year before his death. A to-do list was found in his home. Turing’s mother also believed that his death was not a suicide. One of his biographers, Andrew Hodges, believed that Turing purposely brought the equipment into his room to hide the fact that he did take his own life.
There was one gloomy omen before Turing’s death. Before hid death, he took a trip to a seaside town with friends and met with a fortune teller. A woman who was with him wrote,
“It was a lovely sunny day and Alan was in a cheerful mood and off we went… Then he thought it would be a good idea to go to the Pleasure Beach at Blackpool. We found a fortune-teller’s tent[,] and Alan said he’d like to go in[,] so we waited around for him to come back… And this sunny, cheerful visage had shrunk into a pale, shaking, horror-stricken face. Something had happened. We don’t know what the fortune-teller said[,] but he obviously was deeply unhappy. I think that was probably the last time we saw him before we heard of his suicide.”
There has been an additional conspiracy theory that the British intelligence agencies believed Turing was too big a security threat to be left alive. Turing held a great number of government secrets and he still freely traveled throughout Europe. At the time, there was quite a bit of suspicion placed on gay men.
It took fifty years for the world to start addressing what happened to Alan Turing. In 2009 software engineer John Graham-Cumming began petitioning the British government to make a formal apology for Turing’s criminal charges. After tens of thousands of people signed, British Prime Minister Gordon Brown released a statement that read:
“Thousands of people have come together to demand justice for Alan Turing and recognition of the appalling way he was treated. While Turing was dealt with under the law of the time and we can’t put the clock back, his treatment was of course utterly unfair and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him … So on behalf of the British government, and all those who live freely thanks to Alan’s work I am very proud to say: we’re sorry, you deserved so much better.”
Another petition was started to have Turing formally pardoned. It was originally rejected because homosexuality was illegal at the time he comitted the so-called crime. But politician John Leech continued pushing for the pardon for years. Famous scientists including Stephen Hawking threw their support behind the push. In an unprecedented move, Queen Elizabeth pardoned Alan Turing in 2014.
Public pressure continued to pardon other people who had been convicted of gross indecency and similar crimes. In 2017, The Alan Turing Law pardoned tens of thousands of people. 65,000 men were convicted for homosexual activity before it was decriminalized in England and Wales in 1967.
Turing has been honored many times. Before his death he was made an officer of the order of the British Empire and a Fellow of the Royal Society. There is a street and bridge named after him.
In 1999, Turing was named one of Time magazine’s 100 Most Important People of the 20th Century, writing,
“The fact remains that everyone who taps at a keyboard, opening a spreadsheet or a word-processing program, is working on an incarnation of a Turing machine.”
In 2001, a memorial statue was unveiled. The statue is situated in Manchester, near an area of the city known as its gay village. It pictures Turing holding an apple, which is a little aggressive, but ok. It also says “Founder of Computer Science” and then the same message as if it were sent through an Enigma machine.
It also reads: “Father of computer science, mathematician, logician, wartime codebreaker, victim of prejudice” and “Mathematics, rightly viewed, possesses not only truth, but supreme beauty- a beauty cold and austere, like that of sculpture.”
The sculptor, Richard Humphry, buried his own computer under the sculpture. 2012, 100 years after Turing’s birth, was named Alan Turing Year and featured a year of activities and celebrations of his life around the world. In 2014, a movie was made about cracking the Enigma codes called The Imitation Game, starring Benedict Cumberbatch as Alan Turing.
Breaking the Enigma machine may have shortened World War II by as much as two to four years, saving potentially tens of millions of lives. Alan Turing probably couldn’t have imagined the high esteem that he would be placed in today, especially as an LGBTQ icon. But one of his most famous quotes probably sums it up best. He said:
“We can only see a short distance ahead. But we can see plenty there that needs to be done.”
Thank you for listening to Campfire Stories: Astonishing History. If you enjoyed this show, please don’t forget to subscribe. If you’re listening on a podcast app, I’d love it if you leave a positive review. If you’re listening on YouTube, I encourage you to like this video and leave a comment with an idea for another episode or anything else you’d like to say. If you want to support the show, there’s a link to do that as well. Have a great rest of your day, campers, and I’ll see you back around the campfire soon!
Sources
https://en.wikipedia.org/wiki/History_of_cryptography
https://www.bbc.com/news/uk-37711518
https://en.wikipedia.org/wiki/Enigma_machine
https://en.wikipedia.org/wiki/Cryptanalysis#Ciphers_from_World_War_I_and_World_War_II
http://www.cypher.com.au/crypto_history.htm
https://www.britannica.com/topic/Ultra-Allied-intelligence-project
https://www.theguardian.com/technology/2014/nov/14/how-did-enigma-machine-work-imitation-game
https://www.nature.com/articles/d41586-018-06149-y
https://www.brynmawr.edu/bulletin/codes-and-ciphers-puts-students-test
