Historic gadgets used by British spies will be revealed for the first time later this week, as one of the country's intelligence agencies steps out the shadows to mark its centenary -- and to educate people about the risks of cyber-attacks.
The Government Communications Headquarters (GCHQ) will hold an unprecedented exhibition at London's Science Museum, taking visitors through 100 years of secret conversations and eavesdropping.
It was the codebreakers of GCHQ at Bletchley Park who helped break the Germans' Enigma code during World War II -- as portrayed in the Oscar-winning 2014 film The Imitation Game, starring Benedict Cumberbatch.
A prototype of the Enigma cipher machine used by the Germans will be on display.
But the standout exhibit at this new exhibition is the 5-UCO machine developed in 1943 to send decrypted German messages to officers in the field.
"It was one of the first electronic and fully unbreakable cipher machines and was considered so secret that it was long thought to have been destroyed to conceal the very fact of its existence," GCHQ chief Jeremy Fleming told journalists on Tuesday.
"It turns out we kept one and it's here for everyone to see."
The spy chief said his agency had given unique access to the famous museum in an attempt to tackle the rising threat of cyber crime.
"It is no longer enough for us to serve in secret... openness is our strength," he said.
"We are aiming to put tailored advice in the hands of every citizen," he added.
A laptop infected with the infamous "WannaCry" virus highlights how ordinary citizens can unwittingly act as a gateway for cyber-attacks against major institutions.
This was the virus that brought the computer system of Britain's National Health Service to its knees in 2017.
- Cold War intrigue -
The exhibition begins with a probe of the radio technology used by the nascent GCHQ to calculate the position of German airships attacking Britain in World War I.
It features clothes from crewmen who perished when one was shot down in southern England.
It then showcases infamous encoding devices, such as the Enigma machine, and the ingenious methods that the team at Bletchley Park -- the wartime home of Britain's top code-breakers -- used to crack the code.
A recreation of a humble suburban home near London tells the extraordinary Cold War tale of a Canadian couple who were sending top-secret military information to Moscow on a radio transmitter hidden under their kitchen floor.
And it tackles more recent issues from the digital age, including the revelations by US whistleblower Edward Snowden about the controversial techniques used by GCHQ to intercept communications.
On display is a laptop used by Guardian journalists working on the story -- which intelligence chiefs ordered them to smash up.
"They were happy for us to tell that story," curator Liz Bruton told AFP. "It would be a very odd exhibition not to include that."
They had consulted with academics and civil libertarians about how to approach the issue of security and privacy, she added.
Visitors will be introduced to the capabilities of quantum computing in creating more secure communications -- but also the risks it carries in cracking current systems.
And the hot-button issue of social media is explored through an art installation that churns out real-time Tweets including certain emotive phrases.
"It highlights the amount of data we put out into the world and who has access to that, who owns it," said Bruton.
The final piece reveals the limits to GCHQ's moves towards transparency, displaying dust from pulverized machines used by the agency.
"There are stories we couldn't tell," explained Bruton.
"Top Secret: From Ciphers to Cyber Security" opens to the public on Wednesday and runs until February 2020.