Masking is a widely adopted countermeasure to protect cryptographic implementations from side-channel attacks. Subsequent research has focused on designing masking schemes and formally proving their security, notably through the development of automated tools, within models abstracting the reality of a sidechannel analysis. These designs rely on an external source of randomness; however, there is currently no consensus on the choice of (pseudo-)random number generators for masking. To the...

Classical selection criteria for cryptographic S-boxes—nonlinearity $\mathrm{NL}$, differential uniformity $\delta$, boomerang uniformity $\beta_{\mathrm{B}}$, algebraic degree $\deg$—are invariants of affine equivalence. That property is exactly what blinds them to a class of side-channel weaknesses. The correlation-power-analysis (CPA) template distinguisher is governed by the Hamming-weight functional, and Hamming weight is not affine-invariant; it does not descend to the...

Modern zero-knowledge (ZK), fully homomorphic encryption (FHE) and Multi-party Computation (MPC) protocols have motivated research interest in Arithmetization-Oriented (AO) cryptographic primitives. The use of these protocols on embedded platforms requires consideration for protection against side-channel analysis (SCA), including timing and power attacks. Compared to traditional bit-oriented block ciphers, the design of side-channel countermeasures for AO-based ciphers poses unique...

Post-Quantum Cryptography is now in its deployment phase. Amongst the threats encountered in real-world applications is Side Channel Analysis, a cryptanalysis branch relying on the study of physical leakages from unsecured implementations. However, the FALCON post-quantum signature includes non-linear functions on real numbers, and applying the generic masking countermeasure to these functions has only been recently studied. In this work, we use convergent sequences to approximate the...

Falcon was selected by NIST in 2022 for standardization as a post-quantum digital signature scheme. Among all standardized signature schemes, Falcon achieves the smallest signature size. Its main drawback, however, is its reliance on floating-point arithmetic, which plays a critical role in the security analysis. This reliance poses significant challenges for practical implementations: some platforms lack floating-point units, floating-point division is not constant time on many processors,...

Hamming Quasi-Cyclic (HQC) is a code-based key encapsulation mechanism selected by NIST for standardization, making its resistance to implementation attacks critically important. We present a side-channel attack that exploits load/store leakage in the manipulation of HQC's sparse secret vectors. Analysing Cortex-M4 assembly generated from the reference implementation, we identify a leakage surface in which the low and high 32-bit halves of each 64-bit word...

Side-channel analysis (SCA) attacks rely on leakage from a target device. It is common to assume that linear operations implemented by XOR gates produce symmetric leakage and carry negligible side-channel information. In practice, leakage from XOR gates produces complex, non-independent, and time-varying asymmetric behavior. The paper introduces Feature Estimation based Attacks (FEbA) -- a dedicated profiling attack that exploits these asymmetries. The attack is versatile; it was...

Fixed‑weight sampling is a core primitive in many post‑quantum schemes, including the HQC key encapsulation mechanism. An early implementation of fixed-weight vector sampling in HQC was shown by Guo et al. (CHES 2022) to suffer from a timing side-channel vulnerability, leading to complete key recovery. This timing side-channel was fixed in the current HQC version, however, power side-channel leakage is not addressed. In this work, we demonstrate that fixed-weight vector sampling in HQC...

In reaction to the emerging quantum threat, the National Institute of Standards and Technology (NIST) seeks post-quantum secure digital signature schemes. NIST's ongoing competition recently advanced to the third round, in which the Unbalanced Oil and Vinegar scheme (UOV) is a promising candidate due to UOV's conservative design, small signatures, and performant signing and verification. While these benefits make UOV attractive, the implementation aspects for compact hardware acceleration of...

Edge-AI Internet-of-Things (IoT) devices increasingly perform local neural-network inference in physically accessible environments. While prior physical attacks on neural networks mainly focus on model extraction, parameter recovery, or intermediate computation, the final decision stage remains insufficiently studied. This paper investigates the physical security of ArgMax-based decision logic, which converts output scores into the final class label in many edge-AI deployments. We show that...

With the widespread adoption of Field Programmable Gate Arrays (FPGAs) in security-critical industries such as defense and telecommunications, ensuring the confidentiality of sensitive data processed by these devices has become paramount. Side-Channel Analysis (SCA) poses a significant threat, necessitating the protection of cryptographic primitives through effective and efficient countermeasures. Within the framework of well-established formal adversary models, Boolean masking offers...

Blind side-channel analysis (BSCA) can infer keys without known inputs or outputs, but practical use still needs an upstream step that locates repeated computation and candidate points of interest in an unlabeled trace. We address this trace-only structuring problem with a two-stage method that uses only the per-sample mean and standard deviation, without algorithm labels or metadata. Stage1 estimates a repetition scale, start phase, anchor-supported stable core, and period candidates from...

Modern hardware security heavily relies on the assumption that pre-synthesis algorithmic protections will survive the physical fabrication pipeline. However, untrusted third-party Electronic Design Automation (EDA) toolchains often apply aggressive structural optimizations that can silently compromise perfectly symmetric designs, introducing critical data-dependent power side-channel vulnerabilities. Existing pre-silicon verification methodologies require exposing highly sensitive,...

Bitslice implementations are widely adopted in lightweight cryptography (LWC) due to their efficiency and inherent resilience to side-channel attacks. However, this paper reveals that their decomposition of the S-box exposes critical vulnerabilities to the operation skip fault model. Unlike data corruption faults suffering from high-entropy diffusion, we identify that skipping bitwise operations induces strongly restricted differential patterns. To exploit this characteristic, we...

Cryptographic hardware implementations often leak secret information through side channels. This can allow attackers to learn secret data, such as a cryptographic key, without any vulnerability in the cryptographic algorithm itself. A popular countermeasure to such attacks is masking, which ensures that processed data is independent of the secrets by splitting them into multiple independent shares, often at the cost of significant overhead in terms of required area, latency, and randomness....

Hints are a concept from side-channel analysis referring to small amounts of information that enable an adversary, via a potentially very efficient procedure, to extract the secret. We take this cryptanalytic concept and give it a constructive make-over. We formalize a short $\Sigma$-protocol based on the famous Goldreich, Micali, Wigderson protocol, in which the responses are not of the full witness size, but are only small hints. The hints can be used to extract the full response....

Constant time programming patterns is the primary defense against timing attacks on cryptographic implementations, yet what "constant time" means varies across academia and industry. This work systematizes constant time models and their evolution, identifies a recurring gap between what models protect and what specifications assume, and distills an offensive methodology for discovering timing vulnerabilities that originate outside the cryptographic primitive boundary. Applying this...

End-to-end deep-learning side-channel attacks on public-key implementations have recently become possible even for million-sample traces. However, existing methods require large computational resources and extract only partial key shares, which means that dedicated post-processing is required to turn detected leakage into demonstrations of successful key recovery attacks. We present an end-to-end sequence-to-sequence prediction approach to recover complete 256-bit key shares from single raw...

Unrolled cryptographic hardware architectures are increasingly deployed to maximize throughput, inherently intro- ducing massive algorithmic noise floors that frequently thwart traditional temporal Side-Channel Analysis (SCA). However, the reliance on structural combinational noise as a standalone coun- termeasure remains underexplored against adaptive, AI-driven profiling. This work presents a novel autonomous framework uti- lizing a Large Language Model (LLM) agent to orchestrate...

In this work, we present a generic side-channel protected design of Ascon that achieves high efficiency by dynamically reconfiguring the hardware countermeasures during message processing. The resultant implementation is protected and capable of meeting stringent performance requirements whilst minimising resource overhead. The experimental results obtained demonstrate that the implementation meets the required security and achieves superior throughput-to-area ratio across all protection...

The Learning With Errors (LWE) problem is a cornerstone of lattice-based cryptography and underpins the security of numerous cryptographic schemes. To enhance efficiency, practitioners often employ sparse secrets in LWE, where the secret vector $\mathbf{s}$ has a significantly lower Hamming weight than its dimension $n$. While this approach improves performance, it raises security concerns, particularly against side-channel attacks that can leak partial information, or “hints,” about the...

Masking-based countermeasures such as Threshold Implementations and Probe-Isolating Non-Interference (PINI) are commonly assumed to protect cryptographic software against side-channel leakage by maintaining isolation between secret shares. In this work, we show that this assumption can break on modern out-of-order (OoO) processors due to backend microarchitectural effects that are not visible at the ISA level. We present \texttt{OoOLyzer}, a trace-driven analysis framework that...

Research on cryptographic algorithms implemented in hardware and protected against side-channel attacks has advanced rapidly in recent years. Generalized masking schemes, such as Threshold Implementations (TI) and Domain-Oriented Masking (DOM), currently provide a solid theoretical security foundation. Security models, including the probing model and its various extensions, enable formal verification of these guarantees. In addition, established guidelines for designing securely composable...

This paper presents a side-channel attack on the Linear Equivalence Signature Scheme (LESS) v2.0. LESS derives its security from the Linear Equivalence Problem and was evaluated as a candidate during Round 2 of the NIST post-quantum cryptography standardization process. LESS secret keys are used to generate monomial matrices, which are stored efficiently in two one-dimensional lists: the permutation list and the coefficient list. Recovering the secret monomial matrices is sufficient to forge...

Discrete Gaussian sampling is an important operation at the core of many lattice-based cryptosystems, which presents significant challenges from an implementation standpoint. In particular, it is difficult to protect against side-channel attacks. Extensive research has gone into the problem of addressing timing side-channel attacks, and as result, constant-time discrete Gaussian sampling is now well-understood. However, few papers so far have attempted to achieve protection against...

In side-channel analysis of ML-KEM (a NIST-standard PQC algorithm), SASCA is a powerful profiling attack. However, obtaining a profiling device strictly matching the target is challenging in practice. To address this, we propose the first profiling-device-free SASCA framework for ML-KEM. The framework first controls the NTT input by choosing ciphertexts and trains a leakage model. Subsequently, leveraging the similarity between NTT and INTT, it uses adversarial unsupervised domain adaptation...

Module lattice-based key encapsulation mechanisms (ML-KEM) are susceptible to side-channel-assisted chosen-ciphertext attacks (SCA-CCAs) that exploit leakage from the re-encryption process during decapsulation. These attacks enable adversaries to recover secret keys with hundreds to thousands of oracle accesses, thereby posing a critical threat to the practical deployment of post-quantum cryptography. This paper presents RandInvalidCoeff, a novel and lightweight countermeasure that...

Tosun and Savas (IEEE TIFS'23) proposed a non-profiling power analysis attack on masked ML-KEM, or CRYSTALS-Kyber. Their attack can recover a full secret key of Kyber with 7,000 power traces. Later, Tosun et al. (IEEE Access'24) claimed an improvement over the previous attack with only 550 traces, but the result is not convincing. In particular, their attack does not seem to recover a full secret key of masked Kyber; instead, it recovers only the absolute values for every coefficient of a...

We present Panther, a family of six robust hybrid key encapsulation mechanism (KEM) combiners that pair FrodoKEM (unstructured LWE) with ML-KEM (module-LWE, FIPS 203) so that IND-CCA2 security holds whenever either assumption is hard. The family includes five hardened variants of the textbook combiners—parallel HKDF, SHAKE256 splitkey, sequential chaining, XOR, and nested—each made to satisfy a uniform robustness predicate (transcript binding, domain separation, implicit rejection, length...

Side-channel attacks exploiting Plaintext-Checking Oracles (PCOs) instantiated thanks to the leakage of the re-encryption step taking place during decapsulation are a well-known weakness of ML-KEM. An already wide literature investigated how to efficiently exploit such oracles, leading to easy (full) key recoveries. Somewhat surprisingly, the investigation of how to best instantiate PCOs against ML-KEM's most leaking operations is less investigated, in particular when it comes to...

Side-channel attacks are an important class of security exploits, in which an attacker gains access to confidential data by observing information inadvertently leaked by a system. Writing constant-time code is a common defense against time-based and microarchitectural side-channel attacks. Many approaches have been proposed to automatically verify that a program is constant-time. Sound methods can detect all information leaks but, to efficiently analyze large programs, most of them rely...

Masking is a representative side-channel countermeasure that provides provable security. Among masking schemes, Boolean masking (BM) is widely adopted due to its simple sharing structure, while inner product masking (IPM) and code-based masking (CM) have been studied as alternatives that achieve a higher security order with the same number of shares---a property known as security order amplification in the bit-probing model. Recent work by Gaspoz and Dhooghe (TCHES 2025) proposed an IPM...

Discrete Gaussian sampling (DGS) is a fundamental method for generating random noise in various post-quantum cryptographic key generation and signature schemes. However, DGS has been shown to be highly susceptible to side-channel analysis, and several countermeasures have been developed. Masking, a robust countermeasure, is widely employed to secure these schemes against side-channel attacks. Due to the non-linear arithmetic operations involved, DGS has traditionally been considered...

In a paper presented at CRYPTO18, Reparaz et al. introduce a new model called the ``Tile-Probe-and-Fault-Model''. This model proposes to cover more realistic side-channel attacks by considering so-called ``combined'' attacks, in other words attacks using both side-channel leakage and fault injection. In addition, they introduce CAPA, a combined ``Countermeasure Against Physical Attacks'', which is inspired by an MPC protocol called SPDZ. In this paper, by attacking the original Beaver...

Careful management of shares stored in the architectural, general-purpose register file is an important aspect of software-based implementations of masking, because it can impact the associated side-channel leakage. The erasure of residual shares, i.e., shares whose useful lifetime has expired, is one component of such management: erasing them can, for example, prevent subsequent, unintended share recombination. To support effective share erasure, this work makes two contributions. First,...

Quantum computing threatens classical public key systems and has motivated NIST’s PQC standardization, and within this process HAWK has been submitted as a lattice-based signature scheme. While prior analyses focused on mathematical security, the consequences of side-channel leakage in practical HAWK implementations are less systematically understood. We address this gap by formalizing discrete Gaussian sampler leakage as HAWK with Hint and studying three leakage categories: (i) full...

We study key-schedule design under boundary round-key leakage, namely leakage of the first round key, the last round key, or both end round keys. We propose the nonlinear key-schedule $\mathrm{RK}_i = K \oplus F\bigl(K \oplus T(i)\bigr)$, where $K$ is the master key, $T(i)$ is a public domain separation value, and $F$ is a public SPN-based permutation parameterized by its round count $N_F$. Under the boundary-leakage model considered in this paper, leakage of one end round key yields an...

DATA [22] and Microwalk [23] are two advanced dynamic binary instrumentation (DBI) tools for detecting constant-time (CT) violations in software implementations. This paper presents a comparative evaluation of these tools' findings using a common test setup and several cryptographic implementations that are included in the libraries LibTomCrypt, OpenSSL, and liboqs. Our experiments yield reliable results for symmetric ciphers. For asymmetric cryptographic schemes, however, internal random...

Theoretical treatments of leakage-resilient cryptography typically work under the assumption that the leakage learned by the adversary (e.g., about an n-bit secret key) is arbitrary but bounded, in the sense that the leakage is an l-bit string for some threshold l significantly smaller than n. On the other hand, real-world side-channel attacks on physical implementations of cryptographic protocols produce leakage transcripts that are much longer than n. However, unlike the bounded leakage...

Physical attacks are a well-known threat for otherwise secure implementations of cryptographic algorithms. Although attacks and countermeasures for Side-Channel Analysis (SCA) and Fault-Injection Analysis (FIA) are well studied and individually understood, their combined exploitation and the corresponding countermeasures remain a relatively new area of research. Just recently, Feldtkeller et al. presented Combined Private Circuit (CPC) gadgets at CCS 2022 and CCS 2023 which were the first...

This paper investigates a recent, claimed state-of-the-art attack on the ASCADv2 dataset, a higher-order masked and shuffled AES implementation, which we demonstrate to be a false positive. Despite successful validation using classical metrics, including a converging Guessing Entropy (GE), we prove that the model learned no actual side-channel leakage. Instead, it exploited a statistical bias in the intermediate value distribution. We argue that the usual scoring function used in the GE...

In this paper, we present RISQrypt, the first unified architecture in the literature that implements Kyber (ML-KEM) and Dilithium (ML-DSA), standardized lattice-based Post-Quantum Cryptography (PQC) algorithms, with masking. RISQrypt is a hardware–software co-design framework that integrates dedicated cryptographic accelerators to speed up polynomial arithmetic, hashing, and mask-conversion operations, the latter being one of the primary bottlenecks in masked implementations of lattice-based...

Deep Learning-based Non-profiled Side-Channel Analysis (DL-NSCA) enables automatic feature extraction without a profiling device, but existing approaches mainly target non-linear operations, requiring prior knowledge of the algorithm's unique non-linear structure and computable non-linear intermediate values. These limit applicability in analyzing proprietary or undisclosed implementations and in settings where plaintext/ciphertext are masked by unknown randomness (e.g., tweaks or...

Masking, i.e., computing over secret-shared data, is one of the main counter-measures against side-channel analysis, provably secure in the standard noisy-leakage model. However, all the state-of-the-art security proofs rely on a reduction to a more abstract model called random probing (Eurocrypt’14). As a result, the noise requirements of such proofs must scale with the field size of the circuit which, beyond not reflecting real-world physics of target devices, is often prohibitive,...

Non profiled side-channel attacks aim at exploiting leakage traces from a targeted embedded system to extract secret information, without a priori knowledge on the true leakage model of the device. To automate and simplify attacks, deep learning techniques have thus been introduced in the side-channel community. Most of the works published have mainly explored the use of discriminative models in the profiled or non profiled context. However, the lack of interpretability and explainability of...

The rapid progress of Internet-of-Things (IoT) systems and network protocols has strengthened the demand for digital signature schemes with compact signatures and low computational overhead. However, standardized post-quantum signature schemes, such as ML-DSA, SLH-DSA, and Falcon, incur relatively large signature sizes, which limit their practicality on resource-constrained devices (RCD). To address this challenge, NIST recalled the post-quantum digital signature standardization process. It...

Masking is the standard defense against power-based side-channel analysis (SCA) for cryptographic software, in which sensitive variables are split into independent shares. Although prior work often attributes leakage to microarchitectural effects, architectural interactions alone can already introduce subtle leaks that remain poorly understood. In this work, we propose ISALeak, a target-agnostic framework for analyzing full masked implementations to precisely identify and attribute the root...

Masking, the primary countermeasure against differential power attacks, guarantees formal security under abstract execution models that are violated in modern micro-architectures. Meanwhile, processors with out-of-order micro-architectures are increasingly used for high-assurance tasks, yet their physical side-channel leakage remains poorly characterized, hindering side-channel security on such platforms. In this work, we present the first empirical study of physical power side-channel...

Cryptographic hardware implementations are vulnerable to combined physical implementation attacks, integrating Side-Channel Analysis and Fault-Injection Analysis to compromise their security. Although theoretically sound countermeasures exist, their practical application is often complicated and error-prone, making automated security verification a necessity. Various tools have been developed to address this need, using different approaches to formally verify security, but they are limited...

Post-quantum secure digital signatures based on the MPC-in-the-Head (MPCitH) paradigm, a zero-knowledge (ZK) proof-based construction, are becoming increasingly popular due to their small public key size. However, the development of techniques for protecting MPCitH-based schemes against side-channel attacks remains slow, despite them being critical for real-world deployment. In this work, we adapt the Hypercube-MPCitH framework exploiting its native use of additive secret sharing to enable...

In the field of hardware masking, threshold implementations are a well-known technique that provides glitch-resistant power analysis security. While they guarantee probing security, finding a uniform sharing without additional randomness is difficult, making it challenging to apply to certain functions and, consequently, making it impossible to develop a tool that can straightforwardly generate the masked circuit. Additionally, this approach forces designers to use at least three shares in...

Side-channel analysis (SCA) can recover secret keys by exploiting physical leakages emitted during cryptographic computations. Most SCA techniques, however, require knowledge of the plaintext or ciphertext corresponding to each measured trace, which may be unavailable in realistic adversarial settings. Blind side-channel analysis (Blind SCA), first introduced in 2014, relaxes this requirement, but existing work has mainly targeted S-box nonlinearities. We present a systematic study of blind...

ML-DSA (formerly CRYSTALS-Dilithium), NIST’s primary post-quantum signature standard, is increasingly deployed along with the post-quantum transitions. Yet when the implementations of ML-DSA are deployed in practice, their physical security remains underexplored. In this work, we reveal a new attack surface against ML-DSA by exploiting the leakages from both rejected signing trials and the final accepted signing trial. We present, to the best of our knowledge, the first side-channel attack...

Among the countermeasures against side-channel analysis attacks, masking offers formal security guarantees and composability, yet remains challenging to implement efficiently in hardware due to physical defaults like glitches and transitions. Low-latency masking techniques aim to mitigate the performance penalties but can inadvertently compromise security in certain architectural contexts. In particular, the recently proposed Time Sharing Masking (TSM) technique enables single-cycle masked...

We present the first power side-channel analysis of a Hybrid Homomorphic Encryption (HHE) tailored symmetric encryption scheme. HHE combines lightweight client-side Symmetric Encryption (SE) with server-side homomorphic evaluation, enabling efficient privacy-preserving computation for the client and minimizing the communication overhead. Recent integer-based HHE designs such as PASTA, MASTA, HERA, and Rubato rely on prime-field arithmetic, but their side-channel security has not been...

Despite decades of research in electromagnetic (EM) side-channel analysis (SCA), practical attacks still require manual effort and domain expertise to identify informative probe locations on target devices. Existing approaches rely heavily on exhaustive grid scanning or handcrafted alignment, limiting attack scalability and realism. In this work, we present the first automated and adaptive EM SCA framework that uses particle swarm optimization (PSO) to navigate the probe. Particles are...

Fresh re-keying is a countermeasure against side-channel analysis where an ephemeral key is derived from a long-term key using a public random value. Popular instances of such schemes rely on key-homomorphic primitives, so that the re-keying process is easy to mask and the rest of the (e.g., block cipher) computations can run with cheaper countermeasures. The main requirement for these schemes to be secure is that the leakages of the ephemeral keys do not allow recovering the long-term key....

SQIsign, the only isogeny-based signature competing in the ongoing NIST call for additional signatures, offers the most compact key and signature sizes among all other candidates. It combines isogenies with quaternion arithmetic for its signing procedure. In this work, we address a gap in the current implementation of SQIsign: the absence of constant-time algorithms for quaternion arithmetic. We propose constant-time algorithmic formulations for three fundamental routines in SQIsign's...

Inner product masking is a well-studied masking countermeasure against side-channel attacks. IPM-FD further extends the IPM scheme with fault detection capabilities. However, implementing IPM-FD in software especially on embedded devices results in high computational overhead. Therefore, in this work we perform a detailed analysis of all building blocks for IPM-FD scheme and propose a Masked Processing Unit to accelerate all operations, for example multiplication and IPM-FD specific...

Hamming Quasi-Cyclic (HQC) has recently been selected by NIST, after the Round 4 submission, as a postquantum key encapsulation mechanism (KEM) standard and will soon be widely deployed. Therefore, it is important to ensure its implementation is constant-time, i.e., resistant to side-channel attacks. Existing timing attacks on HQC exploit non-constant-time source code and the decryption that is vulnerable to chosen-ciphertext attacks. These active attacks require constructing thousands of...

We present a generic, automatable framework to reduce the demand for fresh randomness in first-order masked circuits while preserving security in the glitch-extended probing model. The method analyzes the flow of randomness through a circuit to establish security rules based on the glitch-extended probing model. These rules are then encoded as an interference graph, transforming the optimization challenge into a graph coloring problem, which is solved efficiently with a DSATUR heuristic....

The Enhanced ISW (E-ISW) masking scheme, recently proposed at DATE 2024, was introduced as a refinement to the classical ISW construction to restore provable security guarantees in hardware implementations affected by glitches. By enforcing input-complete gate evaluations through the use of artificial delays, E-ISW seeks to mitigate the glitch-induced leakage that compromises standard masking techniques. However, in this work, we demonstrate that this modification is fundamentally...

In our increasingly interconnected world, the security of embedded devices plays a critical role in protecting sensitive information. Evaluating this security requires a meticulous examination of how cryptographic processes are implemented within the hardware of these devices. One widely employed technique for this purpose is Power Side Channel Analysis. At the heart of Correlation Power Side Channel Analysis lies the concept of the power consumption model, which helps to simulate power...

Side-channel attacks can uncover sensitive data by analyzing information leakages of cryptographic hardware devices caused by the power consumption, timing, electromagnetic, glitches, etc. An attack exploiting these leakages is the differential power analysis (DPA). Threshold Implementation (TI), introduced by Nikova et al. [JoC 24(2):292-321, 2011], was proposed to resist DPA on hardware implementations of block ciphers and eliminate information leakage due to glitches. TI is based on...

The Hamming Quasi-Cyclic (HQC) scheme has recently been standardized as a post-quantum key encapsulation mechanism (KEM), emphasizing the importance of efficient and secure hardware realizations on embedded platforms. However, HQC relies heavily on sparse–dense polynomial multiplications, where conventional shift-and-add architectures remain both performance- and security-critical. In FPGA implementations, these multiplications dominate execution time—occupying 59.5%, 56.1%, and 58.3% of the...

As the Hamming Quasi-Cyclic (HQC) cryptosystem was recently selected by NIST for standardization, a thorough evaluation of its implementation security is critical before its widespread deployment. This paper presents single-trace side-channel attacks that recover the full long-term secret key of HQC, experimentally evaluated on a protected Cortex-M4 implementation. We introduce two distinct attacks that significantly advance the state of the art: a passive attack that uniquely models key...

HQC (Hamming Quasi-Cyclic) was selected as the fifth algorithm in the NIST suite of post-quantum cryptographic (PQC) standards. As the only code-based algorithm currently standardized by NIST, HQC offers a good balance between security assurance, performance, and implementation simplicity. Most existing power analyses against HQC are of the SPA style: they can recover secrets with a small number of traces, but can only tolerate limited noise. In this paper, we develop a chosen-ciphertext...

The NIST Post-Quantum Cryptography (PQC) standardization has entered its fourth round, underscoring the critical importance of addressing side-channel attacks (SCA), a dominant threat in real-world cryptographic implementations, especially on embedded devices. This paper presents a novel chosen-ciphertext side-channel attack against CRYSTALS-Kyber (standardized as ML-KEM) implementations with Fisher-Yates shuffled polynomial reduction. We propose an efficient and fault-tolerant key recovery...

Side-channel analysis (SCA) exploits physical leakages such as power consumption or electromagnetic emissions to extract secret information from cryptographic implementations. Leakage model is the critical link between observable physical emanations (e.g., power consumption) and internal cryptographic states. When a leakage model fails to match the device’s underlying physical leakage, even powerful attacks like Correlation Power Analysis (CPA) are rendered ineffective. This fundamental...

Software masking—particularly through threshold implementations—has long been regarded as a foundational defense mechanism against side-channel attacks. These schemes enforce the principles of non-completeness and uniformity, offering provable first-order resistance even under realistic leakage assumptions. However, such assurances were primarily developed under the simplified assumption of scalar or in-order execution, where instruction flow and data dependencies are well-behaved and...

Masking is one of the most widespread countermeasures against side-channel attacks. However, its integration into hardware implementation is subject to physical hazards that can mitigate its security. To counter glitches, the most studied physical hazard, an effective solution is to resynchronize the signals by integrating additional hardware layers into the architecture. However, these solutions have an impact on the performance of the implementation. A solution to avoid these limitations...

Domain-informed deep learning integrates specialized knowledge into deep neural networks through modifications to inputs, architectures, loss functions, or training processes. Such approach is usually employed to improve model performance in low/noisy data regime via domain-specific priors. Side-channel analysis is such a domain and even though straight deep learning has become a powerful tool for profiled side-channel, it still struggles on more complex datasets because of weak signals...

Non profiled attacks aim to recover secret information from a device without prior knowledge of its leakage model. However, most practical non profiled attacks, such as Differential Power Analysis, Correlation Power Analysis, and Linear Regression-based Attacks (LRA), still depend on a priori leakage assumptions. Designing a generic attack that does not rely on any such assumption therefore remains an open problem and has been actively investigated by the side-channel community for more than...

Secret sharing is a foundational cryptographic primitive for sharing keys in distributed systems. In a classical $(n,t)$-threshold setting, it involves a dealer who has a secret, a set of $n$ users to whom shares of the secret are sent, and a threshold $t$ which is the minimum number of shares required to recover the secret. These schemes offer an all-or-nothing security approach where less than $t$ shares reveal no information about the secret. But these guarantees are threatened by...

Algebraic Immunity (AI) is a fundamental property in the security analysis of stream ciphers and Boolean functions, measuring the resistance of a function against algebraic attacks. In this work, we focus on the computation of AI and, more specifically, on its generalization to restricted algebraic immunity, which considers annihilators constrained to specific subsets of $\mathbb{F}_2^n$. While the computation of AI has been studied using methods based on Reed-Muller codes and iterative...

The transition to post-quantum cryptography (PQC) is accelerating due to the potential of quantum computing to compromise classical public-key cryptosystems. While standardized schemes such as CRYSTALS-Kyber, CRYSTALS-Dilithium, and SPHINCS+ offer strong theoretical security, practical deployments remain susceptible to physical-layer vulnerabilities, notably side-channel attacks (SCAs). SCAs exploit unintentional leakages in hardware and software implementations—such as power traces,...

Designing practically secure masked circuits remains a central problem in the field of cryptographic implementation. While most masking schemes have been proven secure in the classical probing model, this model fails to capture more advanced side-channel attacks such as horizontal attacks. In recent years, the community has shifted toward the more realistic random probing model, which offers stronger guarantees. Yet, balancing strong security with practical efficiency continues to be a...

Deep learning-based profiled side-channel analysis (SCA) targeting cryptographic implementations has attracted significant attention in recent years. Generalizable deep learning mechanisms, such as contrastive learning-based profiled SCA (CL-SCA), can enhance the effectiveness of SCA without reliance on specific network architectures and hyperparameters. This independence enables robust adaptation across diverse attack scenarios. Nonetheless, CL-SCA relies heavily on data augmentation and...

Physical attacks pose serious challenges to the secure implementation of cryptographic algorithms. While side-channel analysis (SCA) has received significant attention, leading to well-established countermeasures, fault attacks and especially their combination with SCA (i.e., combined attacks) remain less researched. Addressing such combined attacks often requires a careful integration of masking and redundancy techniques to resist the reciprocal effects of faults and probes. Recent research...

Non-invasive security constitutes an essential component of hardware security, primarily involving side-channel analysis (SCA), with various international standards explicitly mandating rigorous testing. However, current SCA assessments rely on manual expert procedures, causing critical issues: inconsistent results due to expert variability, error-prone multi-step testing, and high costs with IP leakage risks for manufacturers lacking in-house expertise. Automated SCA tools that...

Kyber a.k.a ML-KEM is a quantum-safe Key Encapsulation Mechanism, that has been standardized by NIST under FIPS-203 and will definitely in the coming years be implemented in several commercial products. Following fors instance this report https://radar.cloudflare.com/adoption-and-usage?dateRange=52w, one can notice that since the end of 2024, the post-quantum encrypted share of the HTTPS request traffics has been increasing and is about to reach 50% now. However, the resilience of...

With the advancement of deep learning techniques, Deep Learning-based Non-profiled Side-Channel Analysis (DL-NSCA) can automatically learn and combine features, making it a promising method that can skip the manual and precise selection of Points of Interest (PoIs). Existing DL-NSCA methods assume that the attacker can identify a short leakage interval (usually less than 5000 points) containing PoIs from raw traces (more than 100,000 points) and then feed the leakage interval into the...

Deep learning-based side-channel analysis (DLSCA) has demonstrated remarkable performance over the past few years. Even with limited preprocessing and feature engineering, DLSCA is capable of breaking protected targets, sometimes requiring only a single attack trace. In the DLSCA context, the commonly investigated countermeasures are Boolean masking and desynchronization. While the exact mechanisms of how DLSCA breaks masking are less understood, the core idea behind handling...

Hamming Quasi-Cyclic (HQC) has recently been officially selected for standardization by NIST as a post-quantum KEM alternative to ML-KEM. This milestone raises new requirements, in particular the need to design and deploy secure implementations of the scheme. This paper presents two major contributions to secure HQC against Side-Channel Attacks (SCAs). First, we present a detailed sensitivity analysis of HQC, highlighting the critical variables and critical internal functions that need to...

Physical attacks pose a major challenge to the secure implementation of cryptographic algorithms. Although significant progress has been made in countering passive attacks such as side-channel analysis (SCA), protection against fault attacks is still less developed. One reason for this is the broader and more complex nature of fault attacks, which makes it difficult to create standardized fault evaluation methodologies for countermeasures like those used for SCA. This makes it easier to...

Evaluating the security of a device against side-channel attacks is a difficult task. One prominent strategy for this purpose is to characterize the distribution of the rank of the correct key among the different key hypotheses produced by a maximum likelihood attack, depending on the number of measured traces. In practice, evaluators can estimate some statistics of the rank that are used as security indicators---e.g., the arithmetic and geometric mean rank, the median rank, the...

Deep learning-based side-channel analysis (DLSCA) represents a powerful paradigm for running side-channel attacks. DLSCA, in a state-of-the-art setting, can break multiple targets with a single attack trace, requiring minimal feature engineering. As such, DLSCA is an extremely active research area for both industry and academia. At the same time, due to domain activity, it becomes more difficult to understand the current trends and challenges. In this systematization of knowledge, we...

Remote power analysis is a novel threat to information systems. Under this attack model, the adversary does not require direct physical access to the platform or specialized sensing equipment. Most of the literature in this field deals with advanced acquisition methods and adversarial models. In contrast, side-channel analysis techniques for remote attacks have not been sufficiently explored. We bridge this gap by taking a look at the characteristics of the data recovered from remote power...

HQC is a code-based cryptosystem that has recently been announced for standardization after the fourth round of the NIST post-quantum cryptography standardization process. During this process, the NIST specifically required submitters to provide two kinds of implementation: a reference one, meant to serve lisibility and compliance with the specifications; and an optimized one, aimed at showing the performance of the scheme alongside other desirable properties such as resilience against...

We introduce a new compact and constant-time implementation of the FAEST v1.1 signature scheme that allows it to run in resource-constrained Arm Cortex-M4 microcontrollers under 190M cycles for signing or verifying at level 1 security. The main technique for reducing the memory footprint is a new abstraction to reuse or recompute VOLEs on demand, which reduces memory consumption by at least an order of magnitude.

In this work, we present methods for conducting higher-order non-profiled side-channel attacks on Lattice-Based Cryptography (LBC). Our analysis covers two scenarios: one where the device leakage is known and follows Hamming weight model, and another where the leakage model is not Hamming weight based and unknown to the attacker. We focus on the Post-Quantum Cryptography (PQC) standards, the Dilithium digital signature (i.e. ML-DSA) and the Kyber key encapsulation (i.e. ML-KEM) algorithms....

Deep learning (DL)-based side-channel analysis (SCA) has emerged as a powerful approach for extracting secret information from cryptographic devices. However, its performance often deteriorates when targeting implementations protected by masking and desynchronization-based countermeasures, or when analyzing long side-channel traces. In earlier work, we proposed EstraNet, a Transformer Network (TN)-based model designed to address these challenges by capturing long-distance dependencies and...

This paper introduces the weighted sum correlation analysis method, a profiled higher-order side-channel attack that quantifies the significance of time-domain samples based on a chosen leakage model. We also demonstrate the utility of the Hilbert transform in side-channel analysis, showing how its phase-shifting property can be exploited to construct an effective fused score that combines multiple correlation coefficients into a single metric. We validate the presented method on the...

Statistical Ineffective Fault Attack (SIFA) presents a critical threat to cryptographic implementations by circumventing conventional detection-based countermeasures effective against traditional fault attacks. Particularly, SIFA operates via two mechanisms: SIFA-1 exploits fault effectiveness dependency on target values, while SIFA-2 leverages conditional propagation of faulted values based on sensitive intermediates. Recent studies suggest that, masking, mainly a side-channel protection,...

The ongoing transition to post-quantum cryptography has led to a surge of research in side-channel countermeasures tailored to these schemes. A prominent method to prove security in the context of side-channel analysis is the utilization of the well-established t-probing model. However, recent studies by Hermelink et al. at CCS 2024 demonstrate a simple and practical attack on a provably secure implementation of the Fujisaki-Okamoto transform. In this paper, we present an unsupervised...

Side-channel analysis (SCA) is a persistent threat to security-critical systems, enabling attackers to exploit information leakage. To mitigate its harmful impacts, masking serves as a provably secure countermeasure that performs computing on random shares of secret values. As masking complexity, required effort, and cost increase dramatically with design complexity, recent techniques rely on designing and implementing smaller building blocks, so-called “gadgets.” Existing work on optimizing...

In the last years, Deep Learning algorithms have been browsed and applied to Side-Channel Analysis in order to enhance attack’s performances. In some cases, the proposals came without an indepth analysis allowing to understand the tool, its applicability scenarios, its limitations and the advantages it brings with respect to classical statistical tools. As an example, a study presented at CHES 2021 proposed a corrective iterative framework to perform an unsupervised attack which achieves a...

Side-channel attacks are increasingly recognized as a significant threat to hardware roots of trust. As a result, cryptographic module designers must ensure that their modules are resilient to such attacks before deployment. However, efficient evaluation of side-channel vulnerabilities in cryptographic implementations remains challenging. This paper introduces an open-source framework integrating FPGA designs, power measurement tools, and high-performance side-channel analysis libraries to...

At CRYPTO 2009, Heninger and Shacham presented a branch-and-prune algorithm for reconstructing an RSA private key given a random fraction of its private components. This method has been widely adopted in side-channel attacks, and its complexity is closely related to the specific leakage pattern encountered. In this work, we propose a new leakage model that enables efficient key reconstruction by exploiting a vulnerability in the modular exponentiation invoked by OpenSSL's implementation of...

Constant-time implementations are a cornerstone of secure cryptographic systems, particularly in the context of key exchange protocols and digital signature schemes. These implementations are designed to eliminate timing side-channel vulnerabilities by ensuring that the program’s execution time is independent of secret data. A fundamental building block for achieving constant-time behavior is the conditional move operation. Unlike traditional branching constructs (such as if statements),...