John Graham-Cumming doesn't ping me often, but when he does, I pay attention. His day job is as CTO of security giant Cloudflare, but he is also a lay historian of technology guided by a righteous compass. He is perhaps best known for successfully leading a campaign to force the British government to apologize to legendary computer scientist Alan Turing for prosecuting him for homosexuality and essentially molesting him to death. So when he DMed me to say he had “an awesome story,” he promised “one-off pads! 8-bit computers! Flight attendants smuggle diskettes full of random numbers into South Africa!” I replied.
The story he shared revolves around Tim Jenkin, a former anti-apartheid activist. Jenkin grew up “as a regular racist white South African,” as he put it when I contacted him. But when Jenkin traveled abroad – outside the filters of the police state government – he learned about the brutal repression in his home country, and in 1974 he offered his help to the African National Congress, the banned organization that wanted to overthrow the white regime. He returned to South Africa and started working as an activist, distributing pamphlets. He had always had a penchant for gadgets and was adept at making 'leaflet bombs': devices placed in the street that, when activated, shot anti-government flyers into the air to be dispersed by the wind. Unfortunately, he says, we were 'nicked' in 1978. Jenkin was sentenced to 12 years in prison.
Jenkin has a hacker's mind; as a child he was messing around with gadgets, and as a teenager he dismantled and reassembled his motorcycle. Those skills proved his salvation. While working in the wood shop, he made models of the large keys that unlocked the prison doors. After months of covert work and testing, he and two colleagues walked out of prison and finally arrived in London.
It was the early 1980s and the ANC's efforts were waning. The problem was communication. Activists, especially ANC leaders, were under constant surveillance by South African officials. “The decision was made to bring leaders back to the country to be closer to the activists, but that still required them to be in contact with the outside world,” said Jenkin, who was given a mandate to solve the problem. Rudimentary methods, such as invisible ink and sending codes via touch-tone dialing, were not very effective. They wanted a communications system that was automated and unbreakable. The plan was called Operation Vula.
Working from his small council flat in London's Islington district – nicknamed GCHQ, after Britain's top-secret intelligence service – Jenkins began learning to code. These were the early days of PCs and the equipment was laughably weak by today's standards. Breakthroughs in public key cryptography had been known a few years earlier, but there was no readily available implementation. And Jenkin was suspicious of pre-packaged crypto systems, fearing they might contain backdoors that would allow governments access.
Using a Toshiba T1000 PC running an early version of MS-DOS, Jenkin wrote a system that used the most secure form of crypto, a one-time pad, which scrambles messages character by character using a shared key which is as long as the message itself. Using the program, an activist could type a message on a computer and encrypt it with a floppy disk containing the one-time block of random numbers. The activist could then convert the coded text into audio signals and play them on a tape recorder, which would store them. Then, using a public telephone, the activist could call ANC leaders in London or Lusaka, Zambia, for example, and play the tape. The receiver used a modem with an acoustic coupler to capture the sounds, translate them back to digital signals and decode the message using Jenkin's program.
