If you have ever digitised anything – bank details, your faceID or a text conversation with your mum – you have an encryption key.

This number with thousands of digits acts like a cipher for every “message” that you send over the internet, including online shopping and browsing social media. It is created by multiplying two large prime numbers to produce a third number.

To decrypt your cipher, a hacker must factorise the third number: that is, find those two original prime numbers. This would take a classical computer the same amount of time as the universe’s existence.

But quantum computers can factorise these massive encryption keys increasingly quickly. And, as these quantum computers become faster, the security of every digital system could collapse.

University of Sydney Professor

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