Post-Quantum Cryptography (PQC) algorithms should remain secure even in the presence of quantum computers. Although the security of such schemes is guaranteed at the algorithmic level, real-world implementations often suffer from other vulnerabilities like Side-Channel Analysis (SCA) attacks. This Systematization of Knowledge (SoK) paper investigates SCA attacks targeting implementations of PQC algorithms. This work categorizes attacks from an adversarial perspective to identify the most vulnerable components of the algorithms' implementations and highlights unexplored parts in current implementations. In addition, it reviews and analyzes the efficiency and efficacy of existing countermeasures to SCA attacks in current hardware implementations. This approach helps identify countermeasures that provide broader protection and highlights characteristics needed for future secure implementations. Our findings offer guidance in strengthening existing systems and developing more efficient defenses against side-channel attacks.

Side-channel attacks are a major threat to the security of cryptographic implementations, particularly for small devices that are under the physical control of the adversary. While several strategies for protecting against side-channel attacks exist, these often fail in practice due to unintended interactions between values deep within the CPU. To detect and protect from side-channel attacks, several automated tools have recently been proposed; one of their common limitations is that they only support first-order leakage.

ROCKY is a recently introduced countermeasure against fault attacks for authenticated encryption algorithms. It is based on the random rotation of the internal state. In this work, we evaluate the effectiveness of ROCKY as a countermeasure against side-channel attacks. We implement four different types of FPGA-oriented architectures of Xoodoo: an unprotected version and three different versions protected with ROCKY. Xoodoo is used as round function of Xoodyak, which is a scheme in the NIST lightweight cryptography standardization competition. For the experimental setup, the SAKURA-G target board with Spartan-6 FPGA is used. The evaluation of the results is done through test vector leakage assessment (TVLA). This is the first work looking into the side-channel security of the ROCKY countermeasure.

In the private matching problem, a client and a server each hold a set of n input elements. The client wants to privately compute the intersection of these two sets: he learns which elements he has in common with the server (and nothing more), while the server gains no information at all. In certain applications it would be useful to have a fuzzy private matching protocol that reports a match even if two elements are only similar instead of equal. We consider this fuzzy private matching problem, in a semi-honest environment. First we show that the original solution proposed by Freedman et al. is incorrect. Subsequently we present two fuzzy private matching protocols. The first, simple, protocol has a large bit message complexity. The second protocol improves this, but here the client incurs a $O(n)$ factor time complexity.