If cybercriminals had quantum computers at their disposal today, they would probably be able to break public key cryptography, including the popular RSA encryption. We use it every day, for example in web browsers and HTTPS security certificates of websites, as well as in the system of international bank transfers - SWIFT.

But researchers reassure that we are a long way from creating quantum computers. And work is already underway to ensure information exchange security in the age of quantum computers. Such research will also be conducted in the new International Centre for Theory of Quantum Technologies (ICTQT) at the University of Gdańsk.

ICTQT will be created with funds from the International Research Agendas programme of the Foundation for Polish Science. Nearly PLN 35 million funding has been awarded for 5 years of this centre`s operation.

ALGORITHMS WAIT FOR A COMPUTER

Cryptography promoter Dr. Aleksander Wittlin from the Institute of Physics of the Polish Academy of Sciences in Warsaw explains how to break the RSA algorithm. At present, it is believed that one would have to be able to rapidly break down huge numbers (eg, 500-digit numbers). Now it is only possible to randomly multiply numbers and test solutions. Meanwhile, according to the physicist, "a quantum computer would be able run a parallel process of searching the space of prime numbers". Aleksander Wittlin explains that the bit of an ordinary computer can have a state of either 0 or 1. "And the quantum bit, qubit, can be - to put it simply - in a large number of states simultaneously, they are valid at the same time" - he says.

Shor`s algorithm from the 1990s would allow to break the RSA encryption using a quantum computer. If quantum computers were created, not only the use of RSA would be risky, but so would other modern asymmetric algorithms. This cryptography is used, among other things, to secure transactions with chip-based payment cards, operating system patches, or to authenticate transactions between users of cryptographic currencies (including Bitcoin).

NEW COMPUTERS - NEW CRYPTOGRAPHY

So when quantum computers are finally created, the use of old cryptographic security measures will not guarantee security. That`s why researchers from the recently-established ICTQT are working on cryptographic systems that a quantum computer will not be able to break.

Director of the facility, Prof. Marek Żukowski says in an interview with PAP that the Vernam cipher is an example of a secure encryption. This is the only known unbreakable cryptographic algorithm, regardless of technology. Each character forming a message is encrypted separately, in a random way. The key can only be used once and it must be at least as long as the message. A new set of keys must be delivered to the recipient from time to time. "This is often the job of men in dark glasses with suitcases attached to the wrist with handcuffs, who transport suitcases with keys between embassies" - smiles Prof. Żukowski.

But quantum technologies could allow to speed up the key exchange process, reduce the costs of using the Vernam cipher and popularise this safest possible cryptographic technique.

"Quantum cryptography allows to generate an encryption key at any time, and provide it to both parties of communication. This can be done, for example, via optic fibres" - says the researcher from the University of Gdańsk. He explains that if the cipher is intercepted, both parties will immediately know about it.

Such quantum solutions for the exchange of cryptographic keys are already in use. But there is usually so much noise in the whole key exchange process that a spy can hide in it and steal passwords unnoticed.

Researchers from the University of Gdańsk are working on improving quantum cryptographic technologies. They study the properties of photons that will perform best in the exchange of information. They are also looking for new quantum phenomena that can be used in new technologies. In addition, they are improving random number generators and work on the stability of quantum memory. Work on the new "post-quantum" cryptography is also well underway in other places around the world.

QUANTUM COMPUTERS ARE ON THEIR WAY! BUT TO WHERE?

The "age" of quantum computers is still futurology. Scientists from different corners of the world are still wondering how to build such machines. Only the first quantum computing devices have been created. Their computing power is still laughable - it`s only 10 qubits. "I would call it a quantum abacus" - jokes Prof. Żukowski.

It is very difficult to build larger quantum computing devices. "I the case of quantum computers, the more complicated the device, the higher the risk that the computer will make mistakes" - says the director of the Gdansk centre. It is possible to design a quantum device with a computing power of more than 10 qubits, but such a device would be wrong quite often.

Aleksander Wittlin draws attention to another problem. "The question is: is there a limit to building a quantum computer, above which it will not want to exhibit a quantum behaviour" - says the physicist. While quantum follies occur at the level of particles, it is still unclear whether an object counting thousands or millions of particles could be forced into similar behaviours.

"20 years ago I argued that the creation of such a quantum computer would be absolutely impossible. But quantum engineering has developed so much since then that I am now a little more optimistic. But I think that I will not live to see the day when a quantum computer will be able to do any given computing task. This is equivalent to infinity for me" - says Prof. Żukowski.

Author: Ludwika Tomala

PAP - Science in Poland

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