
PQC Explained – The Pleasure and Vain
Many security architects would undoubtedly agree on the importance of the transition to cryptographic suites resistant to quantum computers. We are talking about so called Post-Quantum Cryptography (PQC). However, they mostly do not have any idea of what they are talking about. This is not so much their fault, since the descriptions of PQC suites are usually either oversimplified, or overly cryptic in themselves. Therefore, we start with an understandable, yet still precise enough, model of ML-KEM and ML-DSA schemes, as the two most prominent algorithms for a key encapsulation and digital signatures, respectively. This is assumed to be the pleasing part. Then come the issues. At first, without any discussion, this is going to be the biggest switch in applied cryptography ever. Much smaller replacements took us decades, still not perfectly finished. It is an open question on how to approach PQC migration in a feasible way. At second, it also took us decades to get rid of implementation faults surrounding contemporary algorithms. Yet, they keep popping up, despite perhaps with somewhat lower measure. We can hardly expect this will be radically better with PQC. Another open question is how to handle this issue properly. At third, there is the retroactive cryptanalysis paradigm, meaning store now – break later, urging us to introduce PQC as soon as possible. Until that time, our regular encrypted communication is nothing but sending open letters to the future. All these aspects warn us our approach shall be fully informed, wise, and realistic, otherwise the whole PQC initiative can easily turn into vain.
Tomáš Rosa
Tomáš holds Ph.D. in cryptology with the Best Doctoral Work Award of Czech Technical University for the year 2004. He actively develops and promotes general mathematical modelling of security systems. Natural applications of this approach are, for instance, the side and covert channels attacks, where he gained notable results. His work helped to improve many world-wide standards, such as: PGP, TLS, EMV payment protocol, Bluetooth, and GNSS. Tomáš is the chief mathematical security architect at the Cryptology and Biometrics Competence Centre of Raiffeisen Bank International group. He also lectures mathematical modelling of security at the Faculty of Mathematics and Physics, Charles University in Prague.