Day: December 26, 2015

Station X – tape 2432

It seems hard to believe now, but in the 80s, we were only just learning about the work that went on at Bletchley Park, the UK’s centre for code breaking during the second world war, where teams of mathematicians, logicians, crossword puzzlers and generally bright people attempted to break the codes used by the German forces, in an effort to help the Allied war effort.

First on this tape, Station X, with the episode The Goose that Laid the Golden Eggs.

This is an excellent documentary about the work of the people at Bletchley park, people like John Herivel, who realised that the German Enigma operators often neglected to fully randomise the machine for the first message of the day, and therefore gave up a vital clue that let the Allied codebreakers decipher the message.

John Herivel

When the German operators had to choose two sets of three random letters to start each message, this was another way in, as some operators always used the same letters – their name, their girlfriend’s name – one even used the name Tom Mix – an American cowboy actor from the 20s. HIT was almost always followed by LER.

One of the things the codebreakers were always on the lookout for were the daily code books, which were the enigma machine settings for each day. Every enigma machine had one of these books, and if you had one, you could decrypt all messages on the enigma.

If you’re familiar with the movie U-571, that was a fictional story about a captured U-boat, but there was a real one, when U-110 attacked a convoy off the coast of Iceland. The support vessel managed to hit the U-boat with a depth charge, and it came to the surface. Georg Hogel, the enigma operator on the U-boat, tells how they were all ordered to leave everything and abandon ship, but he went back for an important book – a book of love poems for his girlfriend.

Georg Hogel

David Balme led a boarding party into the U-boat. Like a real-life Matthew McConaughey.

David Balme

He didn’t know what he was looking for, but he retrieved the naval code book, which enabled Station X to start attacking the naval enigma, and start decoding their transmissions.

The next episode, The Ultra Secret, looks at the problem of keeping the secret that enigma had been broken. Churchill gave orders that the information gained from Ultra, the codename of the intelligence from broken enigma codes, should not be used in such a way to reveal that enigma had broken. The Allied forces weren’t able to prevent a key attack, on the island of Crete, because doing so would reveal Ultra.

Remarkably, at one point during the battle for Crete, a British agent had left behind condemning evidence that could destroy Ultra. A message to the agent from Station X revealed that the British had cracked enigma. The Germans found the message and sent it to Berlin. it was even translated into German, and then simply filed away. Nobody had realised its significance.

One of the weaknesses in enigma was that a particular letter was never encoded as itself – letters were always changed. The Germans often sent the same message day after day – routine reports, for example, so the codebreakers could put the decoded message underneath the message they were deciphering, and if any letters matched, they knew the deciphered message was in the wrong place. Another thing the Germans would do is send random messages, to confuse the codebreakers, One particular message was notable because it didn’t contain a single letter L. They realised this meant the message must have been comprised solely of the letter L repeated over and over again, and knowing this meant they could work out the settings of the machine for that day, and decrypt other messages.

Another trick was to coax the germans into writing specific messages by dropping mines at a particular position at sea. The Germans would send a message giving the grid reference, and the codebreakers then had a ‘crib’ with which they could work out machine settings.

This programme also talks about Alan Turing’s development of a computing machine to work out the day’s settings of the enigma machines.

In the final episode, The War of the Machines, the intelligence war turns, as naval supremo Admiral Von Doenitz changed the naval enigma, and Station X was unable to read them once more. The Americans were getting frustrated at the lack of intelligence, and threatened to take over the codebreaking. But in the end, they sent over Americal codebreakers, who integrated well with the team at Bletchley Park.

Another problem from the team was the development by the Germans of the Lorenz cipher, which was a cipher based on teletype machines. Initially, it was hard to break, operating on a completely different mechanism that enigma, but it was discovered that part of its operation depended on a pseudo-random number generator which was described as ‘more pseudo than random’. In the end it took Station X 3 months to break Lorenz, a machine they had never seen, and they even built their own equivalent machine.

Then we get first-hand testimony from one of the legendary figures of Bletchley Park, Tommy Flowers, who worked as an engineer at the Post Office, who thought he could build a machine that would do much of the codebreakers’ work for them. A machine that would be the world’s first programmable computer, known as Colossus.

Tommy Flowers

After the war, Churchill ordered that Colossus and all the plans destroyed, and Flowers’ place in history as the designed of the first computer was forgotten for many years.

After this programme, the recording stops, just after a brief character ident from Adam and Joe.

Adam and Joe

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