“Security guaranteed by the laws of physics, or why quantum mechanics is the theory that cryptographers have always dreamt of?”

In the hyperconnected world of today, the ability to exchange and

process data in a secure fashion has become a strict necessity. While

we have not seen any major failures of currently used technologies, we

should be aware that our feeling of security is based solely on faith.

All authentication and encryption schemes used nowadays in digital

technologies rely on our assumption that certain mathematical problems

are hard to solve (e.g. factoring large numbers). All such schemes can

be broken if a significant computing power becomes available, a new

faster algorithm is developed or a scalable quantum computer is built.

What makes the situation even more worrying is that these schemes can

be broken retroactively. This means that whenever you send an encrypted

message you must think whether you care about the message remaining

secret in the perspective of 5, 10 or 20 years. Moreover, one can prove

that security against computationally-limited enemies is the best that

classical cryptography can do.

Quantum cryptography relies on quantum mechanics to guarantee security.

In the beginning of the 20th century the quantum revolution led by

Einstein, Schrodinger, Heisenberg, Bohr and other prominent physicists

turned classical physics upside down. They realised that the physics of

small systems (composed of a small number of elementary particles like

photons, electrons, atoms) is entirely different and our everyday

intuition simply does not apply. The particular feature that is useful

for cryptography is the seemingly supernatural property that quantum

systems “know” whether we are looking at them or not. In other words,

there is no way of looking at them without disturbing their physical

state. Clearly, this sounds like a theory that paranoid cryptographers

have always dreamt of. In this talk, we will explore the very basic

concepts of quantum mechanics and their usefulness for cryptography. We

will show how some important cryptographic tasks can be achieved with

security guaranteed by the laws of physics rather than some unproven

computational assumptions. We will learn how Nature truly works at the

very fundamental level and why this remains completely undetected in

our everyday lives.

This lecture is organized by the study association of mathematics and information technology, WISV Christiaan Huygens.