02 | Dead and Alive: Quantum attack

Sometimes you, you get lucky.

You get in the right place at the right time.

As my old thesis advisor said, "Give yourself a chance to get lucky", and I certainly gave myself that chance.

As you can hear, physicist Henry Everett is a cheerful guy, and this is even when he's staring down an existential threat.

In 1994, he was in his early 30s, starting off his scientific career in the US Army, and a colleague got in touch about a paper that had just been written.

It was called, [clears throat] Polynomial Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum Computer.

Henry was a bit lost, and understandably so.

I didn't know enough to understand significantly how, how important this stuff was.

I had to do a lot of homework.

[upbeat music] The issue here that Henry was missing at the time was something called public key encryption.

It's a bit complicated, but it's a system that uses numbers to keep information hidden.

It protects army secrets, confidential government documents, and since the '90s, your information online.

Most public transactions, financial transactions, you buy something from Amazon, for example, you'll notice in the web browser it says HTTPS.

S means secure.

It means you're using something called public key encryption.

It's kind of like a handshake between your computer and the rest of the web.

I've gotta break it to you, though.

It takes a small amount of maths to understand.

[chalk scrapes] Okay, class, here we go.

[chalk scrapes] Say you have two prime numbers.

I'll go with 7 and 11.

When you multiply those numbers, you get a bigger number.

[chalk scrapes] 7 times 11 is 77.

If you're then asked to find the factors of 77, meaning find the two numbers that are multiplied to make 77, it's not that hard to work out that it's 7 times 11, an easy calculation when the numbers are small.

Public key encryption works because the prime numbers that we use are enormous, and so the product is enormous squared.