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50 Things That Made the Modern Economy

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The stories of inventions, ideas and innovations which helped create the economic world

Tim Harford tells the fascinating stories of inventions, ideas and innovations which have helped create the economic world.

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50 Things That Made the Modern Economy: Public Key Cryptography

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Cryptography

11/03/2017 GMT

Public Key Cryptography

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Geeks versus government – the story of public key cryptography

Geeks developed it, and the government tried to control it. But without public key cryptography we would not have the internet as we know it.

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)

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