We present a quantum resource estimation of the Rijndael variants \[ N_b = N_k \in \{4,5,6,7,8\}, \qquad N_r = N_b + 6, \] under the NIST MAXDEPTH quantum cost model. Extending the AES quantum encryption oracle~\cite{ref5} parametrically to arbitrary $N_b = N_k$, we generalize the in-place key schedule, including the single- and double-\texttt{SubWord} cases, the \texttt{ShiftRows} offsets, and the round constants. We implement and verify the resulting oracles using ProjectQ. The...

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...

In this work we propose a novel Boolean lookup-table evaluation methodology over binary CKKS when circuit XORs are kept lazy, i.e., evaluated as additions whose least significant bits remain correct. Our method represents a LUT in the Walsh basis, forms the required parity sums by lazy CKKS additions, and packs them into ciphertext slots. We then use CKKS binary bootstrapping as a refresh step: the StC stage maps the packed lazy parities to MSB-encoded bits, removing the overflow; CtS places...

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....

The AEGIS family of authenticated encryption algorithms is built on a large state whose update function is a cascade of dependent AES rounds. For bitslicing, this looks like the worst possible case. Yet the parallelism is already inside a single update: for example, an AEGIS-128L update applies one AES round to all eight state blocks at once, filling an eight-block bitsliced data path by itself. We describe a sliced representation that keeps the rest of the cipher cheap too and lets...

Homomorphic Advanced Encryption Standard (AES) evaluation refers to evaluating the AES circuit with a fully homomorphic encryption (FHE)-encrypted secret key. Applications include in particular Transciphering, which converts AES-encrypted data into FHE ciphertexts without exposing the secret key. Existing homomorphic AES evaluations show a clear separation between latency-oriented solutions and throughput-oriented solutions. CKKS-based methods exploit massive SIMD parallelism and focus...

The advancement of quantum computing threatens public-key cryptographic algorithms used in TLS connections, such as RSA and ECDHE. The Harvest Now, Decrypt Later (HNDL) attack exposes long-term confidential data to risk even before quantum computers are practically realized, yet a systematic methodology for immediately quantifying the quantum vulnerability of individual TLS connections remains absent. This paper proposes a layered risk scoring model that quantifies the quantum threat...

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...

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...

Existing leakage-resistant AEADs are rarely compatible with {\it single-length key} blockciphers (BCs), i.e., blockciphers with key-length equaling block-length. We present UEDTDM and UEDTMX, two single-length key BC-based leakage-resistant AEAD constructions. Both of them are one-pass with rate $1/4$, use ``partially fixed-key'' BC to maximize {\it practical} efficiency, and gather the strongest level of Grade-3 leakage-resistance (a terminology due to Bellizia et al., CRYPTO 2020)...

The integral-resistance property provides strong arguments against integral distinguishers. Recently, Zeng and Tian proposed a new method to show this property for AES. In this paper, we provide a generalized framework and tool called intres to extend and apply this method to other ciphers with complex linear layers. We derive properties that a cipher must fulfill in order for the method to be applicable. Furthermore, we introduce a degree propagation model which helps us determine the valid...

In this paper, we propose a new widely applicable technique for constructing low-depth S-box circuits, which we call SLICE (Segmented Low‑depth Iterative Circuit Exploration). SLICE reduces circuit depth by partitioning circuits into subcircuits and applying bit-level optimizations. To mitigate the optimization cost of subcircuits with large bit-widths or high AND depth, SLICE temporarily reduces their bit-width during the search, making low-depth circuit construction feasible for various...

Basically, public-key searchable encryption schemes require a linear search time with respect to the total number of ciphertexts. Xu, Wu, Wang, Susilo, Domingo-Ferrer, and Jin (IEEE Transactions on Information Forensics and Security, 2015) introduced Searchable Public-Key Ciphertexts with Hidden Structure (SPCHS). In SPCHS, ciphertexts associated with the same keyword are linked through a hidden structure that can be revealed using a trapdoor. This enables efficient extraction of matching...

Ensuring ciphertext indistinguishability is fundamental to cryptographic security, but empirically validating this property in real implementations and hybrid settings presents practical challenges. The transition to post-quantum cryptography (PQC), with its hybrid constructions combining classical and quantum-resistant primitives, makes empirical validation approaches increasingly valuable. By modeling indistinguishability under chosen-plaintext attack (IND-CPA) games as binary...

To penetrate more rounds with Meet-in-the-Middle (MitM) attack, the neutral words are usually subject to some linear constraints, e.g., Sasaki and Aoki's initial structure technique. At CRYPTO 2021, Dong et al. found the neutral words can be nonlinearly constrained. They introduced a table-based method to precompute and store the solution space of the neutral words, which led to a huge memory complexity. In this paper, we find some nonlinearly constrained neutral words can be solved...

The Grover oracle is the core component of the Grover search algorithm. Instead of constructing a Grover oracle from scratch, we consider the common practice of constructing a Grover oracle from an existing fully functional quantum circuit (FFQC). An FFQC typically performs computations for a primary target and includes ancilla restoration for qubits used as intermediate storage. Although such circuits can be directly integrated into an oracle, we find that this inevitably introduces circuit...

This paper proposes a built-in framework that embeds a dedicated ``Crypto Expert" directly into large language models (LLMs) architecture. As an initial attempt, we design a differentiable proxy tailored to the Advanced Encryption Standard (AES) algorithm, using our customized neuron units, including SoftXOR, SoftLUT and GF conv neurons. These units provide functional equivalence to the AES within the Boolean domain, while enabling stable gradients for backpropagation. By integrating this...

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 focuses on quantum key-recovery attacks on block ciphers. Previous works on quantum differential and truncated differential attacks like [Kaplan et al., ToSC 2016] have shown that classical algorithms for key-recovery, typically based on generating differential pairs and sieving them, can be accelerated by up to a quadratic speedup using variants of quantum search, quantum amplitude amplification, and quantum collision-finding. In this paper, we introduce a new quantum...

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...

Committing security for authenticated encryption (AE) captures the difficulty of constructing a distinct input tuple, including the key, that yields the same ciphertext. This notion is relatively new but has attracted significant attention due to its practical relevance. A promising direction is to design generic transforms that convert any AE scheme into a committing one. A common approach to generic transforms, initiated by the CTX transform (Chan and Rogaway, ESORICS 2022), is to add a...

The Multi-Party Computation (MPC)-in-the-Head (MPCitH) framework enables the construction of post-quantum Digital Signature Algorithms (DSAs), offering competitive public key sizes. However, this comes at a cost of high computational complexity, resulting in high signature generation and verification times. In this work, we propose a compact and efficient hardware accelerator for Mirath, an MPCitH-based DSA and candidate in the ongoing NIST PQC standardization effort. We propose a series...

This work extends the methodology of the Class Elimination Attack (CEA) and the Reference Identities (RI/GRI) used in cryptanalysis for its application to block ciphers like AES and complex SPN variants. Probabilistic results concerning the partitioned key space are generalized to algebraic structures defined over finite fields $ \mathbb{F}_{2^n} $, linking them to the cipher's diffusion and confusion properties. Theorems establishing upper bounds for the expected number of classes to...

Fully Homomorphic Encryption (FHE) is a powerful primitive which allows a computationally weak client to outsource computation to a powerful server while maintaining privacy. However, FHE typically suffers from high ciphertext expansion, meaning that the amount of data the client has to send to the server increases by many orders of magnitude after it is encrypted. To solve this problem, the approach known as transciphering consists in combining symmetric encryption with FHE. The most common...

The meet-in-the-middle (MITM) attack is a powerful cryptanalytic technique leveraging time-memory tradeoffs to break cryptographic primitives. Initially introduced for block cipher cryptanalysis, it has since been extended to hash functions, particularly preimage attacks on AES-based compression functions. Over the years, various enhancements such as superposition MITM (Bao et al., CRYPTO 2022) and bidirectional propagations have significantly improved MITM attacks, but at the cost of...

We present an optimized implementation of the GHASH and POLYVAL authentication algorithms used in AES-GCM and AES-GCM-SIV that eliminates the computational overhead of bit-reversal operations. Our approach computes these universal hash functions directly in bit-reversed representation, matching the native format used by carry-less multiplication instructions available on modern processors. The algorithm exploits 64-bit polynomial primitives and parallel execution on superscalar...

This paper introduces the ALF cipher family, designed for format-preserving encryption. The key strategy is to leverage AES-NI instructions to achieve a high software performance while also providing 128-bit security. A central part of the paper is the design of an AES-related bit-oriented block cipher called ALF-$n$-$t$, with a block size ranging from 16 to 127 bits. The core of the design is byte-oriented, but allows appending up to 7 bits to a byte-oriented input. We introduce an...

In this paper, we aim to explore the design of low-latency authenticated encryption schemes particularly for memory encryption, with a focus on the temporal uniqueness property. To achieve this, we present the low-latency Pseudo-Random Function (PRF) called $\mathtt{Twinkle}$ with an output up to 1152 bits. Leveraging only one block of $\texttt{Twinkle}$, we developed $\texttt{Twinkle-AE}$, a specialized authenticated encryption scheme with six variants covering different cache line sizes...

In this paper, we propose a quantum circuit implementation of AIM2. We apply optimization to reduce the circuit depth and introduce a method to reuse qubits by performing inverse operations in parallel. For all AIM2 variants (AIM2-I, AIM2-III, AIM2-V), we design quantum circuits for $\mathsf{Mer}^{-1}$, the linear layer, $\mathsf{Mer}$, and feed-forward. We confirm that the $\mathsf{Mer}^{-1}$ operation dominates the overall cost. Compared to the previous version of AIM, AIM2 requires...

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...

Symmetric cryptography is confronting threats posed by quantum computing, including Grover's search algorithm and Simon's algorithm. In the fault-tolerant quantum computation, the limited qubit count, connectivity constraints, and error rates of quantum hardware impose stringent requirements on the implementation of cryptographic quantum circuits. Constructing low-resource quantum circuit models forms the foundation for evaluating algorithmic resistance to quantum threats. At CRYPTO 2019,...

The efficiency of circuit implementations for cryptographic algorithms is crucial for their practical deployment. The implementation cost of the linear layer can be evaluated by the number of XOR operations, typically measured in generalized XOR (g-\xor) and serial XOR (s-XOR). Finding the minimal sequence of g-XOR operations constitutes the Shortest Linear Program (SLP) problem. Existing approaches generally address this problem through a two-stage framework: generating an initial sequence...

We introduce the \(Inverse\ Discrete\ Logarithm\ Problem\) (iDLP) framework, which inverts traditional discrete logarithm assumptions by making the exponent public but deliberately non-invertible modulo the group order, while hiding the base. This creates a many-to-one algebraic mapping that is computationally infeasible under both classical and quantum attack models. Within this framework, we define three post-quantum cryptographic primitives: Inverse Discrete Diffie–Hellman (IDDH),...

One of the main layers in the Advanced Encryption Standard (AES) is the substitution layer, where an $8 \times 8$ S-Box is used $16$ times. The substitution layer provides confusion and makes the algorithm resistant to cryptanalysis techniques. Therefore, the security of the algorithm is also highly dependent on this layer. However, the cost of implementing $8 \times 8$ S-Box on FPGA platforms is considerably higher than other layers of the algorithm. Since S-Boxes are repeatedly used in...

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...

This paper studies the security of key derivation functions (KDFs), a central class of cryptographic algorithms used to derive multiple independent-looking keys (each associated with a particular context) from a single secret. The main security requirement is that these keys are pseudorandom (i.e., the KDF is a pseudorandom function). This paper initiates the study of an additional security property, called key control (KC) security, first informally put forward in a recent update to NIST...

In this work, we study the quantum security of key-alternating ciphers (KAC), a natural multi-round generalization of the Even–Mansour (EM) cipher underlying many block cipher constructions, including AES. While the classical security of KAC and the quantum security of the $1$-round KAC (i.e. Even-Mansour) cipher are well understood, the quantum resistance of multi-round KAC remains largely unexplored. We focus on the $2$-round KAC construction, defined using public $n$-bit permutations...

The dream of achieving data privacy during external computations has become increasingly concrete in recent years. Indeed, since the early days of Fully Homomorphic Encryption (FHE) more than a decade ago, new cryptosystems and techniques have constantly optimized the efficiency of computation on encrypted data. However, one of the main disadvantages of FHE, namely its significant ciphertext expansion factor, remains at the center of the efficiency bottleneck of FHE schemes. To tackle the...

Fully Homomorphic Encryption (FHE) enables arbitrary computation directly on encrypted data. The TFHE scheme supports encryption of bits or small integers, evaluating any univariate function via programmable bootstrapping (PBS), which also refreshes ciphertext noise. Since both linear and nonlinear functions can be expressed with PBS, arbitrary circuits of unlimited depth can be computed without accuracy loss, aside from a negligible failure probability. However, a key limitation of TFHE is...

The Estonian i-voting experience, since 2005, is probably the richest to analyze; yet it still holds a collection of noteworthy threats as stated in the 2025 Estonian Academy of Science (Cyber Security Committee) report. This paper first gathers vulnerabilities discovered and improvements/fixes introduced to the Estonian i-voting system, IVXV, in the years 2023-2025; then presents a thorough analysis of its status, as of October 2025 version, with exploits pointed out and solutions...

Advanced Encryption Standard (AES) is one of the most widely used and extensively studied encryption algorithms globally, which is renowned for its efficiency and robust resistance to attacks. In this paper, three quantum circuits are designed to implement the S-box, which is the sole nonlinear component in AES. By incorporating a linear key schedule, we achieve a quantum circuit for implementing AES with the minimum number of qubits used. As a consequence, only 264/328/398 qubits are needed...

Deimos Cipher is a symmetric encryption algorithm designed to achieve high entropy, strong diffusion, and computational efficiency. It integrates HKDF with BLAKE2b for key expansion, ensuring secure key derivation from user-supplied passwords. The encryption process employs XChaCha20, a high-speed stream cipher, to provide strong security and resistance against nonce reuse attacks. To guarantee data integrity and authentication, HMAC-SHA256 is used, preventing unauthorized...

Ongoing efforts to transition to post-quantum public-key cryptosystems have created the need for algorithms with a variety of performance characteristics and security assumptions. Among the candidates in NIST's post-quantum standardisation process for additional digital signatures is FAEST, a Vector Oblivious Linear Evaluation in-the-Head (VOLEitH)-based scheme, whose security relies on the one-wayness of the Advanced Encryption Standard (AES). The VOLEitH paradigm enables competitive...

This paper addresses the critical challenges in designing cryptographic algorithms that achieve both high performance and cross-platform efficiency on ARM and x86 architectures, catering to the demanding requirements of next-generation communication systems, such as 6G and GPU/NPU interconnections. We propose HiAE, a high-throughput authenticated encryption algorithm optimized for performance exceeding 100 Gbps and designed to meet the stringent security requirements of future communication...

With the rapid development of quantum computers, optimizing the quantum implementations of symmetric-key ciphers, which constitute the primary components of the quantum oracles used in quantum attacks based on Grover and Simon's algorithms, has become an active topic in the cryptography community. In this field, a challenge is to construct quantum circuits that require the least amount of quantum resources. In this work, we aim to address the problem of constructing quantum circuits with the...

Physical side-channel analysis (SCA) operates on the foundational assumption of access to known plaintext or ciphertext. However, this assumption can be easily invalidated in various scenarios, ranging from common encryption modes like Cipher Block Chaining (CBC) to complex hardware implementations, where such data may be inaccessible. Blind SCA addresses this challenge by operating without the knowledge of plaintext or ciphertext. Unfortunately, prior such approaches have shown limited...

Making the most of TFHE advanced capabilities such as programmable or circuit bootstrapping and their generalizations for manipulating data larger than the native plaintext domain of the scheme is a very active line of research. In this context, AES is a particularly interesting benchmark, as an example of a nontrivial algorithm which has eluded "practical" FHE execution performances for years, as well as the fact that it will most likely be selected by NIST as a flagship reference in its...

This paper improves upon the quantum circuits required for the Shor's attack on binary elliptic curves. We present two types of quantum point addition, taking both qubit count and circuit depth into consideration. In summary, we propose an in-place point addition that improves upon the work of Banegas et al. from CHES'21, reducing the qubit count – depth product by more than $73\%$ – $81\%$ depending on the variant. Furthermore, we develop an out-of-place point addition by using...

Side-channel analysis (SCA) does not aim at the algorithm's weaknesses but rather its implementations. The rise of machine learning (ML) and deep learning (DL) is giving adversaries advanced capabilities to perform stealthy attacks. In this paper, we propose DL-SCADS, a DL-based approach along with signal decomposition techniques to leverage the power of secret key extraction from post-silicon EM/power side-channel traces. We integrate previously proven effective ideas of model ensembling...

Side-channel attacks exploit information leaked through non-primary channels, such as power consumption, electromagnetic emissions, or timing, to extract sensitive data from cryptographic devices. Over the past three decades, side-channel analysis has evolved into a mature research field with well-established methodologies for analyzing standard cryptographic algorithms like the Advanced Encryption Standard (AES). However, the integration of side-channel analysis with formal methods remains...

The question of whether the complexity class P equals NP is a major unsolved problem in theoretical computer science. The key to proving that P $\neq$ NP is to show that there is no efficient (polynomial time) algorithm for a language in NP. For a language in NP, it is almost impossible to prove that it is not in P, because we can only claim that no better algorithm has been found so far, and there is virtually no way to guarantee (or prove) that a more efficient algorithm does not exist....

In many lightweight cryptography applications, low area and latency are required for efficient implementation. The gate count in the cipher and the circuit depth must be low to minimize these two metrics. Many optimization strategies have been developed for the linear layer, led by the Boyar-Peralta (BP) algorithm. The Advanced Encryption Standard (AES) has been a focus of extensive research in this area. However, while the linear layer uses only XOR gates, the S-box, which is an essential...

Side-Channel Analysis (SCA) exploits physical vulnerabilities in systems to reveal secret keys. With the rise of Internet-of-Things, evaluating SCA attacks has become crucial. Profiling attacks, enhanced by Deep Learning-based Side-Channel Analysis (DLSCA), have shown significant improvements over classical techniques. Recent works demonstrate that ensemble methods outperform single neural networks. However, almost every existing ensemble selection method in SCA only picks the top few...

Chosen-prefix collision (CPC) attack was first presented by Stevens, Lenstra and de Weger on MD5 at Eurocrypt 2007. A CPC attack finds a collision for any two chosen prefixes, which is a stronger variant of collision attack. CPCs are naturally harder to construct but have larger practical impact than (identical-prefix) collisions, as seen from the series of previous works on MD5 by Stevens et al. and SHA-1 by Leurent and Peyrin. Despite its significance, the resistance of CPC attacks has not...

Side-channel attacks pose a serious risk to cryptographic implementations, particularly in embedded systems. While current methods, such as test vector leakage assessment~(TVLA), can identify leakage points, they do not provide insights into their root causes. We propose ARCHER, an architecture-level tool designed to perform side-channel analysis and root cause identification for software cryptographic implementations on RISC-V processors. ARCHER has two main components: (1) Side-Channel...

TFHE is a fully homomorphic encryption scheme over the torus that supports fast bootstrapping. Its primary evaluation mechanism is based on gate bootstrapping and programmable bootstrapping (PBS), which computes functions while simultaneously refreshing noise. PBS-based evaluation is user-friendly and efficient for small circuits; however, the number of bootstrapping operations increases exponentially with the circuit depth. To address the challenge of efficiently evaluating large-scale...

Side-channel attacks (SCAs) remain a significant threat to the security of cryptographic systems in modern embedded devices. Even mathematically secure cryptographic algorithms, when implemented in hardware, inadvertently leak information through physical side-channel signatures such as power consumption, electromagnetic (EM) radiation, light emissions, and acoustic emanations. Exploiting these side channels significantly reduces the attacker’s search space. In recent years, physical...

From 2022, Korean Post-Quantum Cryptography (KpqC) Competition has been held. Among the Round 1 algorithms of KpqC, eight algorithms were selected in December 2023. To evaluate the algorithms, the performance is critical factor. However, the performance of the algorithms submitted to KpqC was evaluated in different development environments. Consequently, it is difficult to compare the performance of each algorithm fairly, because the measurements were not conducted in the identical...

The rectangle attack has shown to be a very powerful form of cryptanalysis against block ciphers. Given a rectangle distinguisher, one expects to mount key recovery attacks as efficiently as possible. In the literature, there have been four algorithms for rectangle key recovery attacks. However, their performance varies from case to case. Besides, numerous are the applications where the attacks lack optimality. In this paper, we delve into the rectangle key recovery and propose a unified and...

Resource-constrained devices such as wireless sensors and Internet of Things (IoT) devices have become ubiquitous in our digital ecosystem. These devices generate and handle a major part of our digital data. However, due to the impending threat of quantum computers on our existing public-key cryptographic schemes and the limited resources available on IoT devices, it is important to design lightweight post-quantum cryptographic (PQC) schemes suitable for these devices. In this work, we...