Quantum computing experts have known for several years that quantum computers will end classical cryptography. One of them, Juan José García Ripoll, a researcher at the Institute of Fundamental Physics of the Higher Council for Scientific Research (CSIC), who conducts his research within the quantum information group and foundations of quantum theory, warned us during our conversation with him in October 2019. That moment arrived in May 2024.
A team of researchers from Shanghai University (China) led by Professor Wang Chao successfully used a D-Wave quantum computer to break the SPN (Substitution-Permutation Network) encryption, which is a cryptographic algorithm used to encrypt information. This encryption is the cornerstone of, for example, the AES (Advanced Encryption Standard) standard, which is widely used. These scientists published the result of their research in an interesting article titled 'Public Key Cryptographic Attack Algorithm Based on Quantum Processing with the Advantage of D-Wave'.
Interestingly, Professor Wang Chao and his team used two strategies to carry out their attack on cryptographic algorithms. The first one broadly consists of providing the quantum computer with a combination of an optimization problem and a search problem. Quantum machines are very efficient at solving these challenges. The second strategy involves combining the Schnorr algorithm, Babai's rounding, and a quantum optimization method. In any case, the most interesting thing is that these Chinese scientists concluded that AES-256 and other military-grade encryption algorithms are closer than ever to being compromised.
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During my conversation with Juan José García Ripoll, I seized the opportunity to ask him what would happen when quantum computers were capable of breaking the most advanced encryption technologies we currently use. 'In principle, quantum computers will make the encryption algorithms we use vulnerable. For this reason, there is a research area in mathematics and cryptography: quantum-resistant cryptography. It is a very difficult field of work. The alternative to the fact that many codes can be broken with quantum computers is to use quantum systems for cryptography.'