Researchers in Waterloo, Ontario, have been exploring lightweight block ciphers for use in embedded systems that require speed and efficiency in encryption. Three such ciphers, PRESENT, GIFT64, and RECTANGLE, have been developed based on an SPN structure for academic purposes. GIFT-128, a component of GIFT-COFB, was a runner-up in the recent NIST lightweight crypto competition, losing to Ascon.
Notably, PRESENT can be found in certain ISO standards, although its usage is limited, and there is uncertainty around the adoption of RECTANGLE. As academic designs, these ciphers have undergone extensive analysis to assess their security and efficacy.
Integral distinguishers, which are essential for breaking encryption schemes used in block ciphers, have been a focus of research. A 2018 study introduced classical computing techniques for finding these distinguishers in various algorithms, including PRESENT, GIFT64, and RECTANGLE.
The paper further explores the use of mixed-integer linear programming (MILP) in solving complex cryptographic problems. By allowing non-integer variables, MILP offers flexibility and efficiency in optimization compared to other methods.
A breakthrough in the research involved the development of a new computational architecture known as Quantum Annealing-Classical Mixed Cryptanalysis (QuCMC). This approach combines quantum annealing algorithms with traditional mathematical methods to analyze symmetric cipher algorithms such as those based on the SPN structure.
Experiments conducted using the D-Wave Advantage quantum computer have successfully identified integral distinguishers up to nine rounds in ciphers like PRESENT, GIFT-64, and RECTANGLE. The use of quantum computing in this context has shown promising results in surpassing traditional heuristic-based global optimization algorithms.
The significance of this research lies in its innovative approach to symmetric cryptanalysis, leveraging quantum computing capabilities to enhance the traditional methods used in breaking encryption. The study does not aim to undermine established encryption standards like AES or RSA but rather introduces a new technique to enhance cryptographic analysis. David Jao, a professor specializing in post-quantum cryptography, likened the research to discovering a new lock-picking method – achieving the same result through a novel approach.