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Mention WW2 code breakers and Alan Turing springs to mind. But he worked alongside several brilliant cryptographers at Bletchley Park, the British Government’s code and cipher unit.
And mathematician William Tutte was one of them
He was born in the small town of Newmarket in the south of England. After studying at Trinity College, Cambridge, he graduated with a degree in Chemistry. And in May 1941, was invited to join the wartime code breaking team based at Bletchley.
THE ENIGMA MACHINE
Alan Turing was already there when Tutte arrived. Turing and his team worked on morse code messages transmitted by the German Enigma machine. And they had discovered the key to reading these messages.
This enabled the Allies to secretly listen in to German military operations. And gave them a huge advantage during the battle against U-boats prowling in the Atlantic.
THE HAGELIN MACHINE
Although interviewed by Turing, Tutte didn’t join his team. Instead, he joined a group led by chief cryptographer, Brigadier John Tiltman.
They were trying to break an Italian naval cipher. They knew it was transmitted by a Swedish built Hagelin machine. And within a few months the team had successfully deciphered it.
TELEPRINTERS AND CODED TAPE
But British radio operators began to intercept an unknown and much faster signal. They identified this as high-speed output from an electronic teleprinter.
Teleprinters used a typewriter-style keyboard to convert messages to coded tape. The tape was then fed through a transmission unit attached to the teleprinter. And messages could be transmitted and received at high speeds.
Much faster than the Enigma output.
The team gave the new message signal the code name ‘Fish.’
And nicknamed the unknown machine ‘Tunny.’
THE LORENZ CODE
And so the Bletchley code breakers started work on these new messages.
The team knew the chances of breaking this new code were very small. The code was much more complex. And they were dealing with a machine they’d never seen.
Progress was frustratingly slow.
That was, until a German officer broke the first rule of message transmission.
The Lorenz team got their first breakthrough in August 1941.
THE STORY OF TWO MESSAGES
It came in the form of a message sent by a German officer based in Greece, to another officer in Austria. It was a large message of 4000 characters.
The receiving operator asked for it to be resent, and this is when two crucial mistakes were made.
The Officer's first mistake was that he simply resent it, instead of transmitting the code using a different setting.
His second was abbreviating words to shorten the message.
It was a gift on a notepad to the Bletchley team.
They now had two copies of a message, sent on the same settings, but with abbreviations in the second version.
The coded messages were passed to the chief cryptographer, British Army officer, Brigadier John Tiltman. And by comparing the two code tapes, he and his team were able to identify the message and cipher key.
It took them only 10 days.
But they still had no idea how to use this form of code. Or what type of machine produced it.
IF YOU CAN IMAGINE IT – YOU CAN BUILD IT
That challenge was handed to William Tutte. He was given a copy of the coded messages and his goal was to identify the machine that could produce and read this type of code.
He and his team noticed patterns and repeated characters in the messages. And from the hole positions on the tape, realized the machine used twelve encoding rotors.
They then applied a combination of mathematical formulas and reverse-engineering to the problem.
Within a few weeks, Tutte and his team had identified the structure and mechanics of the Lorenz machine. And could explain how the cipher wheels operated, and in what order.
All this without having seen the machine.
It was an outstanding breakthrough for the Lorenz code team. And a huge personal success for Tutte.
THE BIRTH OF COLOSSUS
Although they now understood how the machine worked, they still couldn’t decipher the messages.
That’s when engineer Tommy Flowers came up with an idea to build what was the first electronic programmable computer. It was massive and took up almost a complete room at Bletchley.
They aptly named it the Colossus.
It was used to run algorithms created by Tutte and it worked. The team successfully deciphered the Lorenz code just before D-Day.
Unbeknown to Hitler, his unbreakable Lorenz code had been broken. And Allied Intelligence services were now tracking his messages and getting details on his military strategies.
THE LORENZ MACHINE
It wasn’t until after the war, that the Intelligence Service discovered these new messages were produced on a Lorenz machine.
The Enigma unit used by the Luftwaffe and Army had three internal rotors generating encrypted messages. The Navy version used four rotors. And both used a combination of the 26-letter alphabet and morse code.
However, the Lorenz used twelve, and the 32-character Baudot code. This created messages that were much more difficult to decipher.
Intelligence also discovered that Hitler regarded the Enigma machine as vulnerable and outdated. He wanted a code he could use to send top secret information to his generals. A code that was so strong, no-one could break it.
The Lorenz machine was the solution.
And it wasn’t until after D-Day that the Allies were able to get their hands on a working Lorenz unit. An original is now on public display in the Bletchley Park museum, England.
EAVESDROPPING ON THE RUSSIANS
Alan Turing and the Enigma breakthrough became well-known. But very few people knew of William Tutte or the Lorenz cipher codebreaking team.
Tutte’s work went unrecognized. And it was almost 50 years before his contribution to the ending of the war was acknowledged and made public.
Amazingly, details of this crucial code breakthrough remained a secret throughout WW2. And for decades afterwards.
And this was deliberate.
British Intelligence didn’t trust the Russian military. And they didn’t want the Russians to know they’d broken the German Lorenz code. In an ironic twist of fate, this secrecy worked to their benefit.
COLD WAR CODE BREAKERS
At the end of WW2, Russian troops captured several Lorenz units, and used them in the early months of the Cold War to send their own coded transmissions.
But they had no idea that British Intelligence was reading their ‘secret’ messages.
However, these WW2 units were soon replaced by the Russian-built Fialka code machine.
This unit worked on a sequence of ten rotors and could be used to convert messages to code tape or printed cards. The Russians used the Fialka throughout the 1960s and 1970s.
A MOMENT THAT CHANGED WORLD HISTORY
The work of William Tutte and the Lorenz code breakers shortened the Second World War by at least two years. And saved thousands of lives across Europe.
Today the code breakers’ successes are acknowledged as some of the most important achievements in world history.
After the war, Professor Tutte emigrated to Canada, where he died in 2002.