Top Secret: From Ciphers to Cyber Security at the Science Museum
Top Secret
is a new exhibition at London's Science Museum, about codes and code-breaking, and their relevance in the modern world. It's presented in association with GCHQ, the UK’s Intelligence, Security and Cyber agency, and contains many documents and artefacts from their collections. The presentation is mostly chronological from the First World War to the 1980s, and then thematic as it comes into the present day.
Until the early 20th century, codes were relatively weak, as messages had to be encoded by hand, which is slow and error-prone, and anyone who intercepted a message had to break the code by hand too. Intercepting messages was difficult when they were written on paper. The invention of the telegraph in the 19th century provided more opportunities for interception, but still required physical access to the network. The Zimmermann telegram, by which Germany tried to persuade Mexico to declare war on the USA, to deter the Americans from entering the First World War in Europe, is perhaps the most famous example of this. As soon as the war had started, the British had cut the German-owned transatlantic cables, meaning that telegrams from Germany to North America had to go through British-owned cables. The Zimmerman telegram was encoded, but was in a code that the British had broken. The British realised they could use the telegram to convince the USA to declare war on Germany, but it had to be done carefully. The British didn't want the Germans to know that they'd broken the code (because then the Germans would stop using it), and so had to contrive a cover story about having stolen the decoded telegram in Mexico. Initially, many people in the USA believed the telegram was a British forgery, but then Zimmermann (the German civil servant who'd sent it) admitted it was genuine.
The advent of radio made it much easier to send messages, but codes had to become much stronger, because messages can be received by anyone within range, not just the intended recipient. The Germans thought that the Enigma and Lorenz codes that they used in the Second World War were unbreakable in practice (meaning that they could be broken, but it would take so long that any information in the message would no longer be useful). But they underestimated British resourcefulness in stealing their codebooks and building machinery to automate the work, the British willingness to throw people at the parts that couldn't be automated (as many as 10,000 people worked at Bletchley Park, the main site for code-breaking), and their own soldiers' ability to leak information. For instance, it was common for German outposts to send a weather report to headquarters every day at 6AM. So Bletchley Park would often start decoding the day's messages by assuming that messages received at 6AM started with the word "weather" and seeing how far they got on that basis. Curiously, the British used codes that were very similar to Enigma, and the Germans knew this, but didn't bother trying to break them, as they thought it would be a waste of time.
The exhibition moves on to a recreation of part of a house used by the Portland Spy Ring, a team of Soviet agents who stole a lot of information about British nuclear submarines and their weapons in the late 1950s and early 1960s. They used microdots to smuggle out drawings, but also had a radio in their attic for sending Morse code to Moscow. They would prerecord their messages on tape and play the tape at high speed into the transmitter, in an effort to reduce the chances of the British detecting the signal.
GCHQ has two main roles, firstly to provide the UK government with relevant and timely information on what Britain's enemies are doing, and secondly to keep the UK's communications secure from enemies. There is some conflict between these roles, partly because many of the UK's enemies use similar codes to the UK, and partly because some enemies are already in the UK (terrorists and members of criminal gangs). It doesn't help that criminals have a motive to try to break into other people's communications, to get money or information they can exchange for money. Every so often, a politician who doesn't understand mathematics suggests or demands that codes used by the public to keep their online banking and messages secure should have some weakness or back door for GCHQ or MI5 or the police to use. Unfortunately, there's no way to be sure that only authorised people know about or can use the back door. Because the back door has to be in the mathematical definition of the code or in the computer program that implements the code, sooner or later, unauthorised people will find it. Besides, if you were a criminal or a terrorist, would you use a code that you knew or thought the government could read?
(There is a conspiracy theory that the reason encrypted email is so difficult to set up and use is that if only a small amount of email traffic is encrypted, it stands out, and it's relatively easy for the government to store and decrypt all of it. If most or all email is encrypted, it's much harder for the government to figure out which messages are important, and so "they" make sure it's too inconvenient for the casual user. Of course nowadays, most online communication is done through websites and apps, which usually come with encryption built in... but how can you tell if the encryption is really as good as it claims to be?)
Overall, the exhibition gives a good account of codes and code-breaking, and how they've affected the UK in the last hundred years or so. Explanations are pitched at a level that most adults should be able to understand. (Public-key cryptography is hand-waved with a statement to the effect that "the public and private keys are mathematically related.") I was pleased to see all the interactive pieces for small children are tucked into an alcove near the end - scattering them throughout the tour would probably have made it too cramped.
Top Secret runs until 23 February 2020. Admission is free, but advance booking is recommended. Allow an hour to an hour and a half to go round.
Until the early 20th century, codes were relatively weak, as messages had to be encoded by hand, which is slow and error-prone, and anyone who intercepted a message had to break the code by hand too. Intercepting messages was difficult when they were written on paper. The invention of the telegraph in the 19th century provided more opportunities for interception, but still required physical access to the network. The Zimmermann telegram, by which Germany tried to persuade Mexico to declare war on the USA, to deter the Americans from entering the First World War in Europe, is perhaps the most famous example of this. As soon as the war had started, the British had cut the German-owned transatlantic cables, meaning that telegrams from Germany to North America had to go through British-owned cables. The Zimmerman telegram was encoded, but was in a code that the British had broken. The British realised they could use the telegram to convince the USA to declare war on Germany, but it had to be done carefully. The British didn't want the Germans to know that they'd broken the code (because then the Germans would stop using it), and so had to contrive a cover story about having stolen the decoded telegram in Mexico. Initially, many people in the USA believed the telegram was a British forgery, but then Zimmermann (the German civil servant who'd sent it) admitted it was genuine.
The advent of radio made it much easier to send messages, but codes had to become much stronger, because messages can be received by anyone within range, not just the intended recipient. The Germans thought that the Enigma and Lorenz codes that they used in the Second World War were unbreakable in practice (meaning that they could be broken, but it would take so long that any information in the message would no longer be useful). But they underestimated British resourcefulness in stealing their codebooks and building machinery to automate the work, the British willingness to throw people at the parts that couldn't be automated (as many as 10,000 people worked at Bletchley Park, the main site for code-breaking), and their own soldiers' ability to leak information. For instance, it was common for German outposts to send a weather report to headquarters every day at 6AM. So Bletchley Park would often start decoding the day's messages by assuming that messages received at 6AM started with the word "weather" and seeing how far they got on that basis. Curiously, the British used codes that were very similar to Enigma, and the Germans knew this, but didn't bother trying to break them, as they thought it would be a waste of time.
The exhibition moves on to a recreation of part of a house used by the Portland Spy Ring, a team of Soviet agents who stole a lot of information about British nuclear submarines and their weapons in the late 1950s and early 1960s. They used microdots to smuggle out drawings, but also had a radio in their attic for sending Morse code to Moscow. They would prerecord their messages on tape and play the tape at high speed into the transmitter, in an effort to reduce the chances of the British detecting the signal.
GCHQ has two main roles, firstly to provide the UK government with relevant and timely information on what Britain's enemies are doing, and secondly to keep the UK's communications secure from enemies. There is some conflict between these roles, partly because many of the UK's enemies use similar codes to the UK, and partly because some enemies are already in the UK (terrorists and members of criminal gangs). It doesn't help that criminals have a motive to try to break into other people's communications, to get money or information they can exchange for money. Every so often, a politician who doesn't understand mathematics suggests or demands that codes used by the public to keep their online banking and messages secure should have some weakness or back door for GCHQ or MI5 or the police to use. Unfortunately, there's no way to be sure that only authorised people know about or can use the back door. Because the back door has to be in the mathematical definition of the code or in the computer program that implements the code, sooner or later, unauthorised people will find it. Besides, if you were a criminal or a terrorist, would you use a code that you knew or thought the government could read?
(There is a conspiracy theory that the reason encrypted email is so difficult to set up and use is that if only a small amount of email traffic is encrypted, it stands out, and it's relatively easy for the government to store and decrypt all of it. If most or all email is encrypted, it's much harder for the government to figure out which messages are important, and so "they" make sure it's too inconvenient for the casual user. Of course nowadays, most online communication is done through websites and apps, which usually come with encryption built in... but how can you tell if the encryption is really as good as it claims to be?)
Overall, the exhibition gives a good account of codes and code-breaking, and how they've affected the UK in the last hundred years or so. Explanations are pitched at a level that most adults should be able to understand. (Public-key cryptography is hand-waved with a statement to the effect that "the public and private keys are mathematically related.") I was pleased to see all the interactive pieces for small children are tucked into an alcove near the end - scattering them throughout the tour would probably have made it too cramped.
Top Secret runs until 23 February 2020. Admission is free, but advance booking is recommended. Allow an hour to an hour and a half to go round.
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