Fehr is working on quantum information theory, which combines quantum physics and information theory, and its applications to cryptography. Thanks to cryptographic schemes from this information theory, we can now do secure internet banking, for example, and our medical records are secure. These schemes are very difficult to crack with today’s computers. "But if at some point there’s a working quantum computer, much of the current cryptography will be insecure," says Fehr. "And there’s a huge effort going into developing that computer." In the future quantum computers will be able to make rapid calculations that would take regular computers millions of years, such as factoring large integers in the blink of an eye.

Serge Fehr Fehr is therefore working with others to develop and analyse new cryptographic schemes that a quantum computer wouldn’t be able to crack. Fehr: "I’m researching whether the schemes we want to use are as secure as we think they are. And I do that from a very mathematical perspective."

### Mathematics

He has loved mathematics since secondary school. What he likes is how maths takes a lot of intuition and imagination but is ultimately really precise. "You have to translate everything into strict mathematical formulas. And there is nothing in between. A mathematical statement is true or false. What I also really like is that it’s endless. With every mathematical problem that you solve, new problems pop up and ask to be tackled. The abstract and theoretical side of my work motivates me but it’s a nice side-effect that some of what I do helps make our digital world a safer place."

*Source: How quantum mechanics threatens our digital lives – and makes them safer. Dagmar Aarts (UL).*

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