John Graham-Cumming doesn’t text me often, but when he does I pay attention. His day job is CTO of security giant Cloudflare, but he’s also a lay historian of technology, guided by a straight compass. He is perhaps best known for successfully leading a campaign to force the UK government to apologize to legendary computer scientist Alan Turing for prosecuting him for homosexuality and essentially stalking him to death. So when he texted me to tell me he had “an amazing story,” promising “disposable pads! 8-bit computers! “Stewardesses smuggling floppy disks full of random numbers to South Africa!” I replied.
The story he shared centers on Tim Jenkin, a former anti-apartheid activist. Jenkin grew up “as an ordinary racist white South African,” as he described it when I contacted him. But when Jenkin traveled abroad (beyond the filters of the police state government) he learned of the brutal oppression in his home country and in 1974 offered his help to the African National Congress, the banned organization attempting to overthrow the white regime. He returned to South Africa and dedicated himself as an activist, distributing leaflets. He had always had a penchant for gadgets and was an expert at creating “leaflet bombs”—devices placed in the street that, when activated, launched anti-government fliers into the air that were scattered by the wind. Unfortunately, he says, in 1978 “we were robbed.” Jenkins was sentenced to 12 years in prison.
Jenkin has a hacker’s mind: even as a child he played with gadgets, and as a teenager he disassembled and reassembled his motorcycle. Those skills proved his salvation. Working in the carpentry workshop, he created models of the large keys that could open the prison doors. After months of carpentry and surreptitious testing, he and two colleagues broke out of prison and finally arrived in London.
It was the early 1980s and the ANC’s efforts were faltering. The problem was communications. Activists, especially ANC leaders, were under constant surveillance by South African officials. “The decision was made to bring senior leaders back to the country so that they could be closer to the activists, but to do so they still had to be in contact with the outside world,” says Jenkin, who was given the mandate to resolve the problem. Rudimentary methods, such as invisible ink and sending codes via tone dials, were not very effective. They wanted a computerized, unbreakable communication system. The plan was called Operation Vula.
Working out of his small council flat in London’s Islington neighborhood (nicknamed GCHQ, after the top-secret British intelligence agency), Jenkins set about learning to code. These were the early days of PCs and the equipment, by today’s standards, was ridiculously weak. A few years earlier there had been advances in public key cryptography, but there was no readily available implementation. And Jenkin was suspicious of pre-packaged cryptosystems, fearing they could harbor backdoors that would provide access to governments.
Using a Toshiba T1000 computer Running an early version of MS-DOS, Jenkin wrote a system that uses the most secure form of cryptography, a one-time pad, which encrypts messages character by character using a shared key 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 a block of one-time random numbers. The activist could then convert the ciphertext into audio signals and play them back to a recorder, which would store them. Then, using a payphone, the activist could call, say, ANC leaders in London or Lusaka, Zambia, and play the tape. The recipient would use a modem with an acoustic coupler to capture the sounds, translate them back into digital signals, and decrypt the message with Jenkin’s program.