Adam Murphy is back with Elizabeth Bruton at the Science Museum in London to talk spycraft…

Adam - Spycraft and encryption moved on after World War 2 and eventually we landed in the James Bond Cold War era world of spycraft, with spies around every corner, and hidden messages shrunken down on tiny pieces of microfilm. But how ridiculous is that, really?

Elizabeth - The Portland Spy Ring was one of the most successful Soviet spy rings in Britain during the Cold War. It consisted of five people, but the two people we were particularly interested in were Helen and Peter Kroger. They were ostensibly a Canadian couple living in Ruislip in north London, that well-known centre for spying. He was an antiquarian bookseller, she was a housewife, but they were actually American Communists spying on behalf of Soviet Russia. They were using powerful radio sets and microdots. That is where you photograph a document or image and you shrink it down to the size of a full stop so you can send it in books and letters and so on. And they were using those to send top secret naval documents back to Soviet Russia, particularly relating to Britain's nuclear submarine program. The spy ring was detected and then arrested in January 1961. All five members were imprisoned. All of their homes and other locations were searched for the spycraft that they were using. And we have a number of examples on display: we have their radio set which they would have used to communicate with Soviet Russia...

Adam - You still have to hide though. Keep your top secret Soviet spy ring under the radar so to speak. How would you go about keeping yourself secure?

Elizabeth - They believed that by locating themselves in Ruislip that their wireless messages which were sent in high speed Morse code bursts would be undetected because they were near RAF Northolt, which would have had a lot of wireless traffic as well. That wasn't indeed the case, but nonetheless, we still don't know what naval secrets they stole specifically because the documents were taken out, photographed, and then returned. They were all imprisoned, some of them ended up going back to Soviet Russia, but it's a really fascinating piece of Cold War history and one which really captured public attention. There were books and plays about it at the time, newspaper headlines which we've plastered over the outside of a replica of their house. One for example: “Villa was wireless station for a spy ring.” It just really captured people’s public attention and concerns about what spycraft is available, and can you trust people to be who they say they are.

Adam - How would you even know where to look on a document like this if you got your hands on it though?

Elizabeth - They would have hidden it in books or letters that would have gone on a secure route back to Soviet Russia, and they would have sent wireless messages in advance telling people in Russia where to look and where to find it.

Adam - And that would mean the letters could be as innocuous as you like… the message hidden in a full stop.

Elizabeth - Yep. So you know, the letter or the books could have been anything and since Peter Kroger was an antiquarian bookseller, it was quite par for the course for him to be sending books out to all over the world.

Adam - That's the Cold War though, that's a long time ago. When it comes down to the best standards of encryption, the smartest thing to do is to take us humans out of the equation entirely.

Elizabeth - So we're standing in front of a case that contains lots of different objects, modern and not so modern. At the back we have things that look like very small scrabble tiles but they have numbers rather than letters. These were used by Government Code and Cipher School staff at Mansfield College in Oxford, where they created secure systems. And the reason why they had these tiles was that they would put them in a bag and they would encourage staff to take one out, to try and create a randomly generated number in the best way that they had available at the time during the Second World War, in order to create one-time pads and to create secure systems. However what we've learnt since then, and we have other more modern electronic systems here including one used to load keys onto an RAF Typhoon aircraft on loan from the Ministry of Defence, is that human beings, and also computers, are absolutely terrible at generating truly random numbers, strings, and so on. We seem predisposed to patterns. Computers are very good at calculating large numbers and so on, but not great at actually, truly creating randomly generated numbers. So next to that display case we have a chaotic pendulum which is used by internet security company CloudFlare along with other devices that gather information from the environment around them, so they have lava lamps which are on display in the CloudFlare lobby, and they use other environmental measurements to create truly randomly generated numbers which are incredibly hard for computers to break, because there is no pattern to them, because they are utterly random. And some of these are used to underpin the security of the Internet and indeed to keep our communications secure today.