How to prepare for the threat of quantum computers
The dawn of quantum computers threatens to break the security we have relied on for decades. To counter this, Bernardo David, associate professor at the IT University of Copenhagen, is developing information-theoretic cryptography schemes.
Written 30 November, 2025 17:22 by Jari Kickbusch
In 1994, mathematician Peter Shor introduced an algorithm that could crack RSA encryption by factoring large numbers at lightning speed. For decades, RSA and similar systems have been the backbone of digital security, but with Shor’s algorithm, a sufficiently powerful quantum computer could break RSA, ECC, and other widely used cryptographic schemes.
"They first quantum computers already exist, but they are not big and powerful enough to be a real threat yet. However, we better prepare for them to be. It will take many years for us to update the security of all our critical IT systems, and there is a risk that quantum computers will be able to crack the encryption before we are post-quantum secure. That could be a catastrophe because with a powerful quantum computer, you could get access to a lot of very sensitive data," says associate professor at the IT University of Copenhagen, Bernardo David.
The Race for Post-Quantum Security
Governments and tech giants are investing billions in post-quantum security. The U.S. National Institute of Standards and Technology (NIST) finalized new quantum-resistant algorithms in 2024. These standards are now being integrated into products by companies like Microsoft and Google. Europe is moving aggressively too. The EU Quantum Technology Flagship programme, backed by €1 billion, is funding research into quantum-safe networks and cryptography, while the Quantum Secure Networks Partnership is developing secure communication systems for critical infrastructure.
The very foundation of post-quantum security, however, is research. Hence, researchers all over the world are racing to develop post-quantum secure protocols. One of them is Bernardo David.
"Essentially, there are two main approaches to constructing post-quantum secure cryptographic schemes. The first approach builds on computational problems that are assumed to be hard even for a quantum computer. The second approach is using information theoretical techniques that do not rely on computational hardness. Computational hardness is a widely used measure of the difficulty of solving a computational problem, often assessed by the amount of time and resources an algorithm needs to succeed. Information theoretical cryptography is concerned with constructing protocols whose security does not rely on the hardness of any problem at all. It is important to investigate both approaches as each of them enables us to construct different kinds of efficient cryptographic schemes," says Bernardo David, who is using information theoretical techniques in his research:
"The advantage of information theoretical cryptographic protocols is that they can be used to implement advanced tasks – for example, privacy-preserving computation – with high efficiency. This is because the mathematical operations involved in such protocols are more efficient than those needed for protocols that are based on computational hardness."
Post-quantum vs. quantum cryptography
According to Bernardo David, one of the challenges in the field of post-quantum security is the widespread assumption that the threat of quantum computers needs to be countered with quantum cryptography. While quantum cryptography relies on the physical principles of quantum mechanics to create secure communication systems, post-quantum cryptography use mathematical algorithms to create systems that are secure against both classical and quantum computers.
"Although quantum cryptography is a very interesting theoretical research topic, it is not a good solution for all systems. It has limited efficiency and extremely high deployment and maintenance costs. This means that investments in post-quantum cryptography research are really important, not only to construct post-quantum secure schemes for secure communication, but also to develop more advanced protocols for tasks such as electronic voting and privacy-preserving machine learning," Bernardo David ends.
Learn more about Bernardo David's research in information theoretical cryptography:
https://eprint.iacr.org/2025/1464
https://eprint.iacr.org/2023/330 https://eprint.iacr.org/2023/943