In May 1927, years after a British undercover agent caught an officer sneaking into the Communist news office in London, police stormed the Arcos building. The basement was installed with devices to combat intruders and they found a secret room without a door handle, in which workers quickly burned documents.
It may have been dramatic, but the British did not find anything they no longer knew. Instead, the attack was a wake-up call to the Soviets, who found that MI5 had been listening to them for years.
“It was a blunder from the first order,” said Anthony Gleece, who heads the Center for Security and Intelligence Research at Buckingham University. To justify the attack, the prime minister had even read some of the deciphered telegrams in the House of Commons.
The result was that the Russians completely rediscovered the way messages were encrypted. Almost overnight, they switched to “disposable pads.” In this system, the random key is generated by the person sending the message and is shared only with the person receiving it. As long as the key is indeed completely random, the code cannot be cracked. We no longer had to worry about who might hear their messages.
Enter “digital stations” – radio stations that broadcast coded messages to spies around the world. Soon even the British did: if you can’t defeat them, join them, as they say. It is quite difficult to generate a completely arbitrary number, because the system will be inherently predictable – exactly what you are trying to avoid. Instead, the officers in London found an ingenious solution.
They will hang a microphone through the window of Oxford Street and record the traffic. “There may be a bus screaming at the same time as calling a police officer. The sound is unique, it will never happen again, ”says Stupples. Then they would convert this to arbitrary code.
Of course, that didn’t stop people from trying to break them. During World War II, the British realized that they could actually decrypt messages – but would have to touch the disposable pad used to encrypt them. “We found that the Russians used the obsolete sheets of disposable pads as replacement toilet paper in Russian army hospitals in East Germany,” Glees said. Needless to say, British intelligence soon found itself looting the contents of Soviet toilets.