Public Key Cryptography

Public Key Cryptography

Author: BBC World Service March 11, 2017 Duration: 9:13

Take a very large prime number – one that is not divisible by anything other than itself. Then take another. Multiply them together. That is simple enough, and it gives you a very, very large “semi-prime” number. That is a number that is divisible only by two prime numbers. Now challenge someone else to take that semi-prime number, and figure out which two prime numbers were multiplied together to produce it. That, it turns out, is exceptionally hard. Some mathematics are a lot easier to perform in one direction than another. Public key cryptography works by exploiting this difference. And without it we would not have the internet as we know it. Tim Harford tells the story of public key cryptography – and the battle between the geeks who developed it, and the government which tried to control it.

(Photo: Encryption algorithms. Credit: Shutterstock)


Behind every price tag, spreadsheet, and market fluctuation lies a human story of curiosity, accident, and sometimes sheer stubbornness. In 50 Things That Made the Modern Economy, the BBC World Service presents a journey through the seemingly ordinary objects and concepts that quietly built the world we live in. Host Tim Harford goes far beyond dry economic theory, digging into the surprising origins of things like the plow, the bar code, or the limited liability company. Each episode unpacks how a single invention or idea rippled out, reshaping work, society, and global power structures in ways we rarely stop to consider. You’ll hear how the humble receipt fueled commerce, how the shipping container erased distances, and how double-entry bookkeeping enabled empires. This isn't just a history lesson; it's a series of detective stories that connect the dots between a tangible thing and the abstract forces that govern our daily lives. The podcast makes the invisible architecture of our world visible and compelling, revealing the economic fingerprints on everything from your smartphone to your supermarket shelf. Harford’s engaging storytelling transforms complex topics into accessible and genuinely fascinating narratives, reminding us that the modern economy wasn't built by abstract forces alone, but by concrete things dreamed up by people. Tune in to understand not just how the economy works, but how it came to be.
Author: Language: English Episodes: 100

50 Things That Made the Modern Economy
Podcast Episodes
Tally Stick [not-audio_url] [/not-audio_url]

Duration: 9:12
Tally sticks were made from willow harvested along the banks of the Thames in London. The stick would contain a record of the debt. It might say, for example, “9£ 4s 4p from Fulk Basset for the farm of Wycombe”. Fulk Bas…
Passports [not-audio_url] [/not-audio_url]

Duration: 9:13
How much might global economic output rise if anyone could work anywhere? Some economists have calculated it would double. By the turn of the 20th century only a handful of countries were still insisting on passports to…
Intellectual Property [not-audio_url] [/not-audio_url]

Duration: 9:10
When the great novelist Charles Dickens arrived in America in 1842, he was hoping to put an end to pirated copies of his work in the US. They circulated there with impunity because the United States granted no copyright…
Video Games [not-audio_url] [/not-audio_url]

Duration: 9:11
From Spacewar to Pokemon Go, video games – aside from becoming a large industry in their own right – have influenced the modern economy in some surprising ways. Here’s one. In 2016, four economists presented research int…
Cuneiform [not-audio_url] [/not-audio_url]

Duration: 9:09
The Egyptians thought literacy was divine; a benefaction which came from the baboon-faced god Thoth. In fact the earliest known script – “cuneiform” – came from Uruk, a Mesopotamian settlement on the banks of the Euphrat…
Air Conditioning [not-audio_url] [/not-audio_url]

Duration: 9:08
Tim Harford tells the surprising story of air conditioning which was invented in 1902 to counter the effects of humidity on the printing process. Over the following decades “aircon” found its way into our homes, cars and…
Elevator [not-audio_url] [/not-audio_url]

Duration: 9:14
In 1853 Elisha Otis climbed onto a platform which was then hoisted high above a large crowd of onlookers, nervy with anticipation. A man with an axe cut the cable, the crowd gasped, and Otis’s platform shuddered – but it…
Contraceptive Pill [not-audio_url] [/not-audio_url]

Duration: 9:14
The contraceptive pill had profound social consequences. Everyone agrees with that. But – as Tim Harford explains – the pill wasn’t just socially revolutionary. It also sparked an economic revolution, perhaps the most si…
TV Dinner [not-audio_url] [/not-audio_url]

Duration: 9:08
The way educated women spend their time in the United States and other rich countries has changed radically over the past half a century. Women in the US now spend around 45 minutes per day in total on cooking and cleani…
Gramophone [not-audio_url] [/not-audio_url]

Duration: 8:57
“Superstar” economics – how the gramophone led to a winner-take-all dynamic in the performing industry. Elizabeth Billington was a British soprano in the 18th century. She was so famous, London’s two leading opera houses…