Bletchley Park, Enigma and the world’s first electronic computer.




Recent visits to Bletchley Park, the home of the World War 2 code breakers in England highlighted the importance of intelligence and cyber security and provided a unique insight into the short but dramatic history of computing, with implications for us all.
Bletchley also has much to photograph, it has the shabby, run down appearance of most British military bases, as well as many historic electro-mechanical and computing devices and military “kit” apparently abandoned on site!

Up until 1975 the activities at Bletchley were a secret. A team of mathematicians, crossword puzzle experts, engineers (what today we might call “nerds”!) lead initially by the genius, Alan Turing, cracked the “Enigma” code, saved tens of thousands of lives and millions of tons of allied shipping and shortened the war by two years. It was also the birthplace of the electronic computer, developed to crack the more sophisticated ‘Lorentz’ Cypher.

Prior to Poland being invaded in 1939 a team of mathematicians had successfully been decoding 75% of messages sent with a German Enigma machine using a machine they called the “Bombe”. The Germans improved the sophistication of Enigma just before the war however, so the Poles decided to share their knowledge with the French and British. Several of these electro-mechanical “Bombe” devices were built at Bletchley.

‘Bombe’ Machines showing Rear (right) and Front (left)

There were several of these devices that worked in “modulo 26” or base 26 i.e. for the 26 letters of the alphabet. Each wheel has 26 positions. The shot below shots the incredible complexity of these machines. The Enigma cipher was designed so that each message letter could never be encoded as itself, this fact was used to test each proposed solution. The purpose of these machines was to iteratively try solutions over and over again until the correct one is found, where no input letter = output letter. Given the huge number of possibilities this could take days – but it did work!

Complexity of Electro-Mechanical ‘Bombe’ machine

On 9th May 1941 HMS Bulldog depth charged the German U boat U110, it came to the surface and the crew surrendered. An Enigma M3 machine (which had three wheels with 26 letters each) was recovered together with the code book. This was found to be able to enter morse code and had 150,000,000,000,000,000,000 combination’s.

U-boat 110 and HMS Bulldog


The team at Bletchley used this to better understand how the machine worked and to decipher the German Naval Enigma codes. However the Germans added a forth wheel (the M4 Enigma), which took another 9 months to crack.  This helped the allies to locate the U-Boat wolfpacks and re-direct the convoys accordingly. At the same time the Navy realised that its codes were being cracked, and when they introduced more complex ciphers, the German hit rate also reduced significantly.

Worlds first electronic programmable computer
Hitler’s own messages were encrypted with a much more sophisticated cipher machine named “Lorentz”. The Germans thought that it was unbreakable. It had TWELVE wheels of 26 letters, but it was the different rotation pattern of the wheels that made it even harder to crack. The Enigma  had a simple pattern of rotation of one character for the first wheel for each keystroke, until all 26 positions had been used, where upon the next wheel would rotate one character and so on. The Lorentz machine had greater complexity where the wheels would sometimes rotate on each keystoke!

Lorentz Machine with 12 wheels

A radio operator’s mistake in sending two very similar messages with the same machine settings enabled a brilliant mathematician, William Tutte to work out its architecture. Bletchley built a machine that simulated the Lorentz operation, called the “Tunny machine”.

‘Tunny’ Machine used to simulate the Lorentz Cipher

Tutte then worked with TJ Flowers to build a valve-based electronic computer to crack the codes. This was called Colossus due to its size and was built in 1943, pre-dating the US built ENIAC by 3 years.

Colossus paper tape reader

Colossus’ most important decipher was a message from Hitler dismissing the idea of a possible Normandy invasion, he was convinced the allies would attack at Calais – he had swallowed the allies deception campaign. This information enabled Montgomery and Eisenhower (later US President) to make the decision to launch the D-Day landings. Based on an idea by mathematician Max Newman and built by Engineer TJ Flowers. Colossus 1 had 1800 valves and Colossus 2 2400, replacing electro-mechanical switches of previous devices. This key step was the birth of the modern computer era.
Tommy Flowers could not cash in on his computer invention, as Churchill insisted that it was kept secret. Most of them were later destroyed. A fully operational Colossus machine has incredibly been rebuilt from scratch by computer expert Tony Sale. See a video of it working hereNote the paper tape reader and optical reader – rather like a CD! The speed of the paper tape determines the speed of the computer.

Bletchley is now a museum open to the public, housing the code breaking equipment and also the National Museum of Computing, with the Colossus as its centerpiece. Tracking the development of computing power since the “valve era” is very interesting. The early computers used valves acting as switches, later machines used discrete transistors and then finally transistors etched onto the silicon chips used by all modern computers. The power of the computer is related to the number of “switches”. 1943 Colossus – 2400, 1946 ENIAC 18000, 1950’s

The huge ENIAC computer used for military purposes

The later IBM Transistor mainframe in the 1960’s had 40000 transistors and filled a large room. The silicon chip microcomputers such as the first IBM PC had 29000 transistors, bu this increased dramatically through different generations of Intel chip until the Pentium 4 processor which had 160 Million transistors, and the Intel Hexacore 2010 1.17 Billion! This is in the current MacPro desktop computer and has the computing power of a 1990’s mainframe. The iphone is more powerful than early PCs.

I can think of no other technology that has gone through such a quantum leap in capability – and scaling down in size in such a short time. It is almost frightening to think of what will happen next!
The world has been transformed by technology in this time. Computers are now personal mobile communications devices, always connected, and the culture of today – particularly of the young is to share information online. Unfortunately robust security has not been built into those devices or networks and there are armies of people trying to break into them and steal data from you and your companies. This is not just troublesome geeks anymore, it is a state sponsored activity, the so called “Advanced Persistent Threat” is real and just like in World War 2 – it is worth billions.

There are lessons we can learn from the World War 2 code breakers.
1.There is no such thing as an unbreakable code – better encryption takes longer and is more expensive to break. It is an “arms race” between code sophistication and computing power to decipher – Do you even encrypt emails sent over the internet? How secure is the data on a lost laptop – is whole disk encryption employed?
2. Human error is the most likely way of compromising information. Inappropriate use of USB sticks has recently been shown to be disastrous for the target. (see “Stuxnet”). Does your company block or monitor USB devices, or email sent to and from internet email accounts? How do you enforce policies?
3. The Lorentz example shows that a simple error can completely compromise integrity. It is critical to recognise once this has happened and act accordingly to recover the situation. The Germans had no idea that Lorentz had been compromised.

Footnote: the collage at the top is comprised of 6 images, overlaid on top of each other using Photoshop layers and masks, I demonstrate how I achieve this in my lecture “Layers & Masks“.


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