Constructing a committing authenticated encryption (AE) satisfying the CMT-4 security notion is an ongoing research challenge. We propose a new mode KIVR, a black-box conversion for adding the CMT-4 security to existing AEs. KIVR is a generalization of the Hash- then-Enc (HtE) [Bellare and Hoang, EUROCRYPT 2022] and uses a collision-resistant hash function to generate an initial value (or nonce) and a mask for redundant bits, in addition to a temporary key. We ob- tain a general bound...

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...

Vistrutah is a large block cipher with block sizes of 256 and 512 bits. It iterates a step function that applies two AES rounds to each 128-bit block of the state, followed by a state-wide cell permutation. Like Simpira, Haraka, Pholkos, and ASURA, Vistrutah leverages AES instructions to achieve high performance. For each component of Vistrutah, we conduct a systematic evaluation of functions that can be efficiently implemented on both Intel and Arm architectures. We therefore expect...

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...

Integral and ultrametric integral cryptanalysis are generalized to finite rings of prime characteristic $p$ that are isomorphic to a product of fields. This extends, for instance, the complete state of the art in integral cryptanalysis from $\mathbf{F}_2^n$ to $\mathbf{F}_q^n$, for all prime powers $q$. A compact representation of transition matrices, based on convex polyhedra, is introduced to ensure that the proposed methods are computationally efficient even for large $p$. Automated...

In this paper, we introduce SCMAC, a general framework that transforms large-memory stream ciphers into AEAD schemes. It represents an intermediate design paradigm between Encrypt-then-MAC and dedicated single-pass AEAD, partially integrating encryption and authentication mechanisms while mitigating the risk of state leakage associated with immediate absorption and squeezing. Consequently, this approach harmonizes high performance with enhanced security. Additionally, we propose LOL2.0, an...

We give new constructions of pseudorandom functions (PRFs) computable in $\mathsf{NC}^1$ from (variants of the) Learning Parity with Noise (LPN) assumption. Prior to our work, the only $\mathsf{NC}^1$-computable PRF from LPN-style assumptions was due to Boyle et al. (FOCS 2020) who constructed a weak PRF from a new heuristic variant of LPN called variable-density LPN. We give the following three results: (1) A weak PRF computable in $\mathsf{NC}^1$ from standard LPN. (2) A...

The security of block ciphers such as AES-128, AES-192, and AES-256 relies on the assumption that their ciphertext outputs are computationally indistinguishable from random permutations. While distinguishers have been proposed for reduced-round variants or under non-standard models such as known-key or chosen-key settings, no effective distinguisher has been demonstrated for the full-round AES ciphers in the standard secret-key model. This work introduces FESLA (Feature Enhanced...

Proxy re-encryption (PRE) is a powerful primitive for secure cloud storage sharing. Suppose Alice stores encrypted datasets (ciphertexts) in a cloud server (proxy). If Bob requests data sharing, Alice shares the ciphertexts by computing and sending a re-encryption key to the proxy, which will perform the re-encryption operation that generates the ciphertexts that are decryptable to Bob. Still, the proxy cannot access the plaintexts/datasets. Traditionally, the re-encryption key can convert...

Masking is one of the most prevalent and investigated countermeasures against side-channel analysis. As an alternative to the simple (e.g., additive) encoding function of Boolean masking, a collection of more algebraically complex masking types has emerged. Recently, inner product masking and the more generic code-based masking have proven to enable higher theoretical security properties than Boolean masking. In CARDIS 2017, Poussier et al. connected this ``security order amplification''...

AES has cemented its position as the primary symmetric-key primitive for a wide range of cryptographic applications, which motivates the analysis on the concrete security of AES in practical instantiations, for instance, the collision resistance of AES-based hashing, the key commitment security of AES-based authenticated encryption schemes, and the one-wayness of AES-based one-way functions in ZK and MPC protocols. In this work, we introduce single-color initial structures (SCIS) into...

Authenticated encryption with associated data (AEAD) schemes are responsible for securing increasingly critical digital infrastructures, worldwide. Unfortunately, current widely deployed schemes suffer from various limitations that make them difficult to use securely in practice. For example, schemes like AES-GCM limit the amount of data that can be encrypted with a single key, therefore limiting its secure scaling to modern workloads. At the same time, practitioners may not be able to move...

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 and unlimited computations directly on encrypted data. Notably, the TFHE scheme allows users to encrypt bits or small numbers (4-6 bits) and compute any univariate function using programmable bootstrapping (PBS), while simultaneously refreshing the ciphertext noise. Since both linear and non-linear functions can be evaluated using PBS, it is possible to compute arbitrary functions and circuits of unlimited depth without any accuracy loss....

AES-GCM has been the status quo for efficient symmetric encryption for decades. As technology and cryptographic applications evolved over time, AES-GCM has posed some challenges to certain use-cases due to its default 96-bit nonce size, 128-bit block size, and lack of key commitment. Nonce-derived schemes are one way of addressing these challenges: Such schemes derive multiple keys from nonce values, then apply standard AES-GCM with the derived keys (and possibly another 96-bit nonce). The...

Safeguarding cryptographic implementations against the increasing threat of Side-Channel Analysis (SCA) attacks is essential. Masking, a countermeasure that randomizes intermediate values, is a cornerstone of such defenses. In particular, SCA-secure implementation of AES, the most-widely used encryption standard, can employ Boolean masking as well as multiplicative masking due to its underlying Galois field operations. However, multiplicative masking is susceptible to vulnerabilities,...

Screaming-channel attacks enable Electromagnetic (EM) Side-Channel Attacks (SCAs) at larger distances due to higher EM leakage energies than traditional SCAs, relaxing the requirement of close access to the victim. This attack can be mounted on devices integrating Radio Frequency (RF) modules on the same die as digital circuits, where the RF can unintentionally capture, modulate, amplify, and transmit the leakage along with legitimate signals. Leakage results from digital switching activity,...

In this paper, we present a side-channel attack on the hardware AES accelerator of a Bluetooth chip used in millions of devices worldwide, ranging from wearables and smart home products to industrial IoT. The attack leverages information about AES computations unintentionally transmitted by the chip together with RF signals to recover the encryption key. Unlike traditional side-channel attacks that rely on power or near-field electromagnetic emissions as sources of information, RF-based...

Power side-channel (PSC) vulnerabilities present formidable challenges to the security of ubiquitous microelectronic devices in mission-critical infrastructure. Existing side-channel assessment techniques mostly focus on post-silicon stages by analyzing power profiles of fabricated devices, suffering from low flexibility and prohibitively high cost while deploying security countermeasures. While pre-silicon PSC assessments offer flexibility and low cost, the true nature of the power...

The Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) delivers both confidentiality and integrity yet poses performance and security challenges on resource-limited microcontrollers. In this paper, we present an optimized AES-GCM implementation for the ARM Cortex-M4 that combines Fixslicing AES with the FACE (Fast AES-CTR Encryption) strategy, significantly reducing redundant computations in AES-CTR. We further examine two GHASH implementations—a 4-bit Table-based approach and a...

The key collision attack was proposed as an open problem in key-committing security in Authenticated Encryption (AE) schemes like $\texttt{AES-GCM}$ and $\texttt{ChaCha20Poly1305}$. In ASIACRYPT 2024, Taiyama et al. introduce a novel type of key collision—target-plaintext key collision ($\texttt{TPKC}$) for $\texttt{AES}$. Depending on whether the plaintext is fixed, $\texttt{TPKC}$ can be divided into $\texttt{fixed-TPKC}$ and $\texttt{free-TPKC}$, which can be directly converted into...

In this paper, we propose a new 10-bit S-box generated from a Feistel construction. The subpermutations are generated by a 5-cell cellular automaton based on a unique well-chosen rule and bijective affine transformations. In particular, the cellular automaton rule is chosen based on empirical tests of its ability to generate good pseudorandom output on a ring cellular automaton. Similarly, Feistel's network layout is based on empirical data regarding the quality of the output S-box. We...

Fault attacks pose a significant threat to cryptographic implementations, motivating the development of countermeasures, primarily based on a combination of redundancy and masking techniques. Redundancy, in these countermeasures, is often implemented via duplication or linear codes. However, their inherent structure remains susceptible to strategic fault injections bypassing error checks. To address this, the CAPA countermeasure from CRYPTO 2018 leveraged information-theoretic MAC tags for...

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...

The introduction of shared computation architectures assembled from heterogeneous chiplets introduces new security threats. Due to the shared logical and physical resources, an untrusted chiplet can act maliciously to surreptitiously probe the data communication between chiplets or sense the computation shared between them. This paper presents Garblet, the first framework to leverage the flexibility offered by chiplet technology and Garbled Circuits (GC)-based MPC to enable efficient,...

We consider the problem of constructing efficient pseudorandom functions with Beyond-Birthday-Bound (BBB) security from blockciphers. More specifically, we are interested in variable-output-length pseudorandom functions (PRF) whose domain is twice that of the underlying blockcipher. We present two such constructions, $\textsf{Pencil}$ and $\sharp\textsf{Pencil}$, which provide weak PRF and full PRF security, respectively, where both achieve full $n$-bit security. While several recent works...

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...

Recent applications and attacks have highlighted the need for authenticated encryption (AE) schemes to achieve the so-called committing security beyond privacy and authenticity. As a result, several generic solutions have been proposed to transform a non-committing AE scheme to a committing one, for both basic unique-nonce security and advanced misuse-resistant (MR) security. We observe that all existing practical generic transforms are subject to at least one of the following limitations:...

The public comments received for the review process for NIST (SP) 800-38A pointed out two important issues that most companies face: (1) the limited security that AES can provide due to its 128-bit block size and (2) the problem of nonce-misuse in practice. In this paper, we provide an alternative solution to these problems by introducing two optimally secure deterministic authenticated encryption (DAE) schemes, denoted as DENC1 and DENC2 respectively. We show that our proposed constructions...

The wide adoption of deep neural networks (DNNs) raises the question of how can we equip them with a desired cryptographic functionality (e.g, to decrypt an encrypted input, to verify that this input is authorized, or to hide a secure watermark in the output). The problem is that cryptographic primitives are typically designed to run on digital computers that use Boolean gates to map sequences of bits to sequences of bits, whereas DNNs are a special type of analog computer that uses linear...

Fully Homomorphic Encryption (FHE) allows computations on encrypted data without requiring decryption, ensuring data privacy during processing. However, FHE introduces a significant expansion of ciphertext sizes compared to plaintexts, which results in higher communication. A practical solution to mitigate this issue is transciphering, where only the master key is homomorphically encrypted, while the actual data is encrypted using a symmetric cipher, usually a stream cipher. The server...

In block ciphers, the attacker should not be able to distinguish a block cipher from a random permutation; therefore the existence of a distinguisher is important. Cryptanalysis of the reduced-round variants of block ciphers is also important in cryptographic design. AES is the most widely used block cipher, and currently, the best-known distinguisher for 5-round AES has a data and time complexity of $2^{29.95}$ with a success probability of 55\%. In this paper, we propose the massive...

The ChaCha20-Poly1305 AEAD scheme is widely used as an alternative for AES-GCM on platforms without AES hardware instructions. Although recent analysis by Degabriele et al. shows that ChaCha20-Poly1305 provides adequate security in the conventional multiuser model, the construction is totally broken when a single nonce is repeated – a real-word scenario that can occur due to faulty implementations or the desire to use random nonces. We present a new nonce-misuse resistant and...

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...

We propose the first $\textit{distributed}$ version of a simple, efficient, and provably quantum-safe pseudorandom function (PRF). The distributed PRF (DPRF) supports arbitrary threshold access structures based on the hardness of the well-studied Learning with Rounding (LWR) problem. Our construction (abbreviated as $\mathsf{PQDPRF}$) practically outperforms not only existing constructions of DPRF based on lattice-based assumptions, but also outperforms (in terms of evaluation time) existing...

In modern cryptography, relatively few instantiations of foundational cryptographic primitives are used across most cryptographic protocols. For example, elliptic curve groups are typically instantiated using P-256, P-384, Curve25519, or Curve448, while block ciphers are commonly instantiated with AES, and hash functions with SHA-2, SHA-3, or SHAKE. This limited diversity raises concerns that an adversary with nation-state-level resources could perform a preprocessing attack, generating a...

We propose efficient, post-quantum threshold ring signatures constructed from one-wayness of AES encryption and the VOLE-in-the-Head zero-knowledge proof system. Our scheme scales efficiently to large rings and extends the linkable ring signatures paradigm. We define and construct key-binding deterministic tags for signature linkability, that also enable succinct aggregation with approximate lower bound arguments of knowledge; this allows us to achieve succinct aggregation of our signatures...

Boolean formula minimization is a notoriously hard problem that is known to be $\varSigma_2^P$-complete. Circuit minimization, typically studied in the context of a much broader subject known as synthesis and optimization of circuits, introduces another layer of complexity since ultimately those technology-independent epresentations (e.g., Boolean formulas and truth tables) has to be transformed into a netlist of cells of the target technology library. To manage those complexities, the...

Meet-in-the-middle (MitM) is a powerful approach for the cryptanalysis of symmetric primitives. In recent years, MitM has led to many improved records about key recovery, preimage and collision attacks with the help of automated tools. However, most of the previous work target $\texttt{AES}$-like hashing where the linear layer is an MDS matrix. And we observe that their automatic model for MDS matrix is not suitable for primitives using a binary matrix as their linear layer. In this...

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...

The CKKS scheme is traditionally recognized for approximate homomorphic encryption of real numbers, but BLEACH (Drucker et al., JoC 2024) extends its capabilities to handle exact computations on binary or small integer numbers. Despite this advancement, BLEACH's approach of simulating XOR gates via $(a-b)^2$ incurs one multiplication per gate, which is computationally expensive in homomorphic encryption. To this end, we introduce XBOOT, a new framework built upon BLEACH's blueprint but...

Unprotected cryptographic implementations are vulnerable to implementation attacks, such as passive side-channel attacks and active fault injection attacks. Recently, countermeasures like polynomial masking and duplicated masking have been introduced to protect implementations against combined attacks that exploit leakage and faults simultaneously. While duplicated masking requires $O(t * e)$ shares to resist an adversary capable of probing $t$ values and faulting $e$ values, polynomial...

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 so-called Gaussian template attacks (TA) is one of the optimal Side-Channel Analyses (SCA) when the measurements are captured with normal noise. In the SCA literature, several optimizations of its implementation are introduced, such as coalescence and spectral computation. The coalescence consists of averaging traces corresponding to the same plaintext value, thereby coalescing (synonymous: compacting) the dataset. Spectral computation consists of sharing the computational workload...

We introduce a new approach between classical security proofs of modes of operation and dedicated security analysis for known cryptanalysis families: General Practical Cryptanalysis. This allows us to analyze generically the security of the sum of two keyed permutations against known attacks. In many cases (of course, not all), we show that the security of the sum is strongly linked to that of the composition of the two permutations. This enables the construction of beyond-birthday bound...

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...

The notion of space hardness serves as a quantitative measure to characterize the resilience of dedicated white-box schemes against code-lifting attacks, making it a widely utilized metric in the field. However, achieving strong space hardness (SSH) under the adaptively chosen-space attack model (ACSAM) remains an unresolved challenge, as no existing white-box scheme has given SSH guarantees under ACSAM. \par To address the problem, we introduce a novel mode of operation tailored for...

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...

For a finite field $\mathbb{F}$ of size $n$, the (patched) inverse permutation $\operatorname{INV}: \mathbb{F} \to \mathbb{F}$ computes the inverse of $x$ over $\mathbb{F}$ when $x\neq 0$ and outputs $0$ when $x=0$, and the $\operatorname{ARK}_K$ (AddRoundKey) permutation adds a fixed constant $K$ to its input, i.e., $$\operatorname{INV}(x) = x^{n-2} \hspace{.1in} \mbox{and} \hspace{.1in} \operatorname{ARK}_K(x) = x + K \;.$$ We study the process of alternately applying the...

In two recent papers, we introduced and studied the notion of $k$th-order sum-freedom of a vectorial function $F:\mathbb F_2^n\to \mathbb F_2^m$. This notion generalizes that of almost perfect nonlinearity (which corresponds to $k=2$) and has some relation with the resistance to integral attacks of those block ciphers using $F$ as a substitution box (S-box), by preventing the propagation of the division property of $k$-dimensional affine spaces. In the present paper, we show that this...

Authenticated encryption (AE) is a cryptographic mechanism that allows communicating parties to protect the confidentiality and integrity of messages exchanged over a public channel, provided they share a secret key. In this work, we present new AE schemes leveraging the SHA-3 standard functions SHAKE128 and SHAKE256, offering 128 and 256 bits of security strength, respectively, and their “Turbo” counterparts. They support session-based communication, where a ciphertext authenticates the...

Tweakable enciphering modes (TEMs) provide security in various storage and space-critical applications, including disk and file-based encryption and packet-based communication protocols. XCB-AES (originally introduced as XCBv2) is specified in the IEEE 1619.2 standard for encryption of sector-oriented storage media and comes with a formal security proof for block-aligned messages. In this work, we present the first plaintext recovery attack on XCB-AES $-$ the shared difference attack,...

There has been a recent interest to develop and standardize Robust Authenticated Encryption (Robust AE) schemes. NIST, for example, is considering an Accordion mode (a wideblock tweakable blockcipher), with Robust AE as a primary application. On the other hand, recent attacks and applications suggest that encryption needs to be committing. Indeed, committing security isalso a design consideration in the Accordion mode. Yet it is unclear how to build a Robust AE with committing security....

Datasets of side-channel leakage measurements are widely used in research to develop and benchmark side-channel attack and evaluation methodologies. Compared to using custom and/or one-off datasets, widely-used and publicly available datasets improve research reproducibility and comparability. Further, performing high-quality measurements requires specific equipment and skills, while also taking a significant amount of time. Therefore, using publicly available datasets lowers the barriers...

In this paper, we explore a new type of key collisions called target-plaintext key collisions of AES, which emerge as an open problem in the key committing security and are directly converted into single-block collision attacks on Davies-Meyer (DM) hashing mode. For this key collision, a ciphertext collision is uniquely observed when a specific plaintext is encrypted under two distinct keys. We introduce an efficient automatic search tool designed to find target-plaintext key collisions....

We present a tweakable wide block cipher called Mystrium and show it as the fastest such primitive on low-end processors that lack dedicated AES or other cryptographic instructions, such as ARM Cortex-A7. Mystrium is based on the provably secure double-decker mode, that requires a doubly extendable cryptographic keyed (deck) function and a universal hash function. We build a new deck function called Xymmer that for its compression part uses Multimixer-128, the fastest universal hash for...

In this work, we study constant round multiparty computation (MPC) for Boolean circuits against a fully malicious adversary who may control up to $n-1$ out of $n$ parties. Without relying on fully homomorphic encryption (FHE), the best-known results in this setting are achieved by Wang et al. (CCS 2017) and Hazay et al. (ASIACRYPT 2017) based on garbled circuits, which require a quadratic communication in the number of parties $O(|C|\cdot n^2)$. In contrast, for non-constant round MPC, the...

The RISC-V Vector Cryptography Extensions (Zvk) were ratified in 2023 and integrated into the main ISA manuals in 2024. These extensions support high-speed symmetric cryptography (AES, SHA2, SM3, SM4) operating on the vector register file and offer significant performance improvements over scalar cryptography extensions (Zk) due to data parallelism. As a ratified extension, Zvk is supported by compiler toolchains and is already being integrated into popular cryptographic middleware such as...

At Asiacrypt 2022, a holistic key guessing strategy was proposed to yield the most efficient key recovery for the rectangle attack. Recently, at Crypto 2023, a new cryptanalysis technique--the differential meet-in-the-middle (MITM) attack--was introduced. Inspired by these two previous works, we present three generic key recovery attacks in this paper. First, we extend the holistic key guessing strategy from the rectangle to the differential attack, proposing the generic classical...

The see-in-the-middle (SITM) attack combines differential cryptanalysis and the ability to observe differential patterns in the side-channel leakage traces to reveal the secret key of SPN-based ciphers. While SITM presents a fresh perspective to side-channel analysis and allows attacks on deeper cipher rounds, there are practical difficulties that come with this method. First, one must realize a visual inspection of millions of power traces. Second, there is a strong requirement to reduce...

Side-channel analysis (SCA) has posed a significant threat to systems for nearly three decades. Numerous practical demonstrations have targeted everyday devices, such as smartcards, cryptocurrency wallets, and smartphones. However, much of the research in the public domain has focused on low-end microcontrollers, limiting our understanding of the challenges involved in attacking more complex systems. In this work, we conduct a reality check on SCA by targeting a high-performance ARM...

Due to the ubiquitous requirements and performance leap in the past decade, it has become feasible to execute garbling and secure computations in settings sensitive to side-channel attacks, including smartphones, IoTs and dedicated hardwares, and the possibilities have been demonstrated by recent works. To maintain security in the presence of a moderate amount of leaked information about internal secrets, we investigate {\it leakage-resilient garbling}. We augment the classical privacy,...

Clarifying the robustness of authenticated encryption (AE) schemes, such as security under nonce misuse or Release of Unverified Plaintext (RUP), is critically important due to the extensive use of AEs in real-world applications. We present a comprehensive analysis of the robustness of well-known standards, namely GCM, CCM, and OCB3. Despite many existing studies, we uncovered several robustness properties for them that were not known in the literature. In particular, we show that both...

Robust message authentication codes (MACs) and authenticated encryption (AE) schemes that provide authenticity in the presence of side-channel leakage are essential primitives. These constructions often rely on primitives designed for strong leakage protection, among others including the use of strong-unpredictable (tweakable) block-ciphers. This paper extends the strong-unpredictability security definition to the versatile and new forkcipher primitive. We show how to construct secure and...

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...

Secure multi-party computation (MPC) enables multiple distrusting parties to jointly compute a function while keeping their inputs private. Computing the AES block cipher in MPC, where the key and/or the input are secret-shared among the parties is important for various applications, particularly threshold cryptography. In this work, we propose a family of dedicated, high-performance MPC protocols to compute the non-linear S-box part of AES in the honest majority setting. Our...

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...

We propose a new NTRU-based Public-Key Encryption (PKE) scheme called $\mathsf{NTRU+}\mathsf{PKE}$, which effectively incorporates the Fujisaki-Okamoto transformation for PKE (denoted as $\mathsf{FO}_{\mathsf{PKE}}$) to achieve chosen-ciphertext security in the Quantum Random Oracle Model (QROM). While $\mathsf{NTRUEncrypt}$, a first-round candidate in the NIST PQC standardization process, was proven to be chosen-ciphertext secure in the Random Oracle Model (ROM), it lacked corresponding...

The recent VOLE-based interactive zero-knowledge (VOLE-ZK) protocols along with non-interactive zero-knowledge (NIZK) proofs based on MPC-in-the-Head (MPCitH) and VOLE-in-the-Head (VOLEitH) extensively utilize the commitment schemes, which adopt a circular correlation robust (CCR) hash function as the core primitive. Nevertheless, the state-of-the-art CCR hash construction by Guo et al. (S&P'20), building from random permutations, can only provide 128-bit security, when it is instantiated...

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...

Side-channel-analysis (SCA) resistance with cost optimization in AES hardware implementations remains a significant challenge. While traditional masking-based schemes offer provable security, they often incur substantial resource overheads (latency, area, randomness, performance, power consumption). Alternatively, the RAMBAM scheme introduced a redundancy-based approach to control the signal-to-noise ratio, and achieves exponential leakage reduction as redundancy increases. This method...

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...

Physical attacks, and among them fault injection attacks, are a significant threat to the security of embedded systems. Among the means of fault injection, laser has the significant advantage of being extremely spatially accurate. Numerous state-of-the-art studies have investigated the use of lasers to inject faults into a target at run-time. However, the high precision of laser fault injection comes with requirements on the knowledge of the implementation and exact execution time of the...

The use of Internet of Things (IoT) devices in embedded systems has become increasingly popular with advancing technologies. These devices become vulnerable to cyber attacks as they gain popularity. The cryptographic operations performed for the purpose of protection against cyber attacks are crucial to yield fast results in open networks and not slow down network traffic. Therefore, to enhance communication security, studies have been conducted in the literature on using asymmetric...

Advanced Encryption Standard in Galois/Counter Mode (AES-GCM) is the most widely used Authenticated Encryption with Associated Data (AEAD) algorithm in the world. In this paper, we analyze the use of GCM with all the Initialization Vector (IV) constructions and lengths approved by NIST SP 800-38D when encrypting multiple plaintexts with the same key. We derive attack complexities in both ciphertext-only and known-plaintext models, with or without nonce hiding, for collision attacks...

This work describes vulnerabilities in the specification of AEAD modes and Key Wrap in two cryptographic message formats. Firstly, this applies to AEAD packets as introduced in the novel LibrePGP specification that is implemented by the widely used GnuPG application. Secondly, we describe vulnerabilities in the AES-based AEAD schemes as well as the Key Wrap Algorithm specified in the Cryptographic Message Syntax (CMS). These new attacks exploit the possibility to downgrade AEAD or AES Key...

We reduce the number of bit operations required to implement AES to a new minimum, and also compute improvements to elements of some other ciphers. Exploring the algebra of AES allows choices of basis and streamlining of the nonlinear parts. We also compute a more efficient implementation of the linear part of each round. Similar computational optimizations apply to other cryptographic matrices and S-boxes. This work may be incorporated into a hardware AES implementation using minimal...

Garbled circuits (GC) are a secure multiparty computation protocol that enables two parties to jointly compute a function using their private data without revealing it to each other. While garbled circuits are proven secure at the protocol level, implementations can still be vulnerable to side-channel attacks. Recently, side-channel analysis of GC implementations has garnered significant interest from researchers. We investigate popular open-source GC frameworks and discover that the AES...

An oblivious pseudorandom function (OPRF) is a two-party protocol in which a party holds an input and the other party holds the PRF key, such that the party having the input only learns the PRF output and the party having the key would not learn the input. Now, in a threshold oblivious pseudorandom function (TOPRF) protocol, a PRF key K is initially shared among T servers. A client can obtain a PRF value by interacting with t(≤ T) servers but is unable to compute the same with up to (t − 1)...

The Impossible Boomerang Attack (IBA) has shown significant power in evaluating the security of block ciphers, such as AES. However, current studies still lack foundational theory, user guild and universal method for constructing IBDs. This paper addresses these gaps through comprehensive research. Theoretically, we establish a new framework for constructing a series of IBDs by differential propagation, state propagation, and generalized boomerang tables. We rigorously prove their inclusion...

The boomerang attack is a cryptanalytic technique which allows combining two short high-probability differentials into a distinguisher for a large number of rounds. Since its introduction by Wagner in 1999, it has been applied to many ciphers. One of the best-studied targets is a 6-round variant of AES, on which the boomerang attack is outperformed only by the dedicated Square attack. Recently, two new variants of the boomerang attack were presented: retracing boomerang (Eurocrypt'20) and...

Masking is a widely adopted countermeasure against side-channel analysis (SCA) that protects cryptographic implementations from information leakage. However, current masking schemes often incur significant overhead in terms of electronic cost. RAMBAM, a recently proposed masking technique that fits elegantly with the AES algorithm, offers ultra-low latency/area by utilizing redundant representations of finite field elements. This paper presents a comprehensive generalization of RAMBAM and...

Key blinding produces pseudonymous digital identities by rerandomizing public keys of a digital signature scheme. It provides privacy in decentralized networks. Current key blinding schemes are based on the discrete log assumption. Eaton, Stebila and Stracovsky (LATINCRYPT 2021) proposed the first post-quantum key blinding schemes from lattice assumptions. However, the large public keys and lack of QROM security means they are not ready to replace existing solutions. We present a general...

Key blinding produces pseudonymous digital identities by rerandomizing public keys of a digital signature scheme. It is used in anonymous networks to provide the seemingly contradictory goals of anonymity and authentication. Current key blinding schemes are based on the discrete log assumption. Eaton, Stebila and Stracovsky (LATINCRYPT 2021) proposed the first key blinding schemes from lattice assumptions. However, the large public keys and lack of QROM security means they are not ready to...

Software based cryptographic implementations provide flexibility but they face performance limitations. In contrast, hardware based cryptographic accelerators utilize application-specific customization to provide real-time security solutions. Cryptographic instruction-set extensions (CISE) combine the advantages of both hardware and software based solutions to provide higher performance combined with the flexibility of atomic-level cryptographic operations. While CISE is widely used to...

The current cryptographic frameworks like RSA, ECC, and AES are potentially under quantum threat. Quantum cryptographic and post-quantum cryptography are being extensively researched for securing future information. The quantum computer and quantum algorithms are still in the early developmental stage and thus lack scalability for practical application. As a result of these challenges, most researched PQC methods are lattice-based, code-based, ECC isogeny, hash-based, and multivariate...

We present a novel approach to small area and low-latency first-order masking in hardware. The core idea is to separate the processing of shares in time in order to achieve non-completeness. Resulting circuits are proven first-order glitch-extended PINI secure. This means the method can be straightforwardly applied to mask arbitrary functions without constraints which the designer must take care of. Furthermore we show that an implementation can benefit from optimization through EDA tools...

Masking is one of the most popular countermeasures to protect implementations against power and electromagnetic side channel attacks, because it offers provable security. Masking has been shown secure against d-threshold probing adversaries by Ishai et al. at CRYPTO'03, but this adversary's model doesn't consider any physical hardware defaults and thus such masking schemes were shown to be still vulnerable when implemented as hardware circuits. To addressed these limitations glitch-extended...

Recent attacks and applications have led to the need for symmetric encryption schemes that, in addition to providing the usual authenticity and privacy, are also committing. In response, many committing authenticated encryption schemes have been proposed. However, all known schemes, in order to provide s bits of committing security, suffer an expansion---this is the length of the ciphertext minus the length of the plaintext---of 2s bits. This incurs a cost in bandwidth or storage. (We...

Differential-linear cryptanalysis was introduced by Langford and Hellman in 1994 and has been extensively studied since then. In 2019, Bar-On et al. presented the Differential-Linear Connectivity Table (DLCT), which connects the differential part and the linear part, thus an attacked cipher is divided to 3 subciphers: the differential part, the DLCT part, and the linear part. In this paper, we firstly present an accurate mathematical formula which establishes a relation between...

While masking is a widely used defense against passive side-channel attacks, its secure implementation in hardware continues to be a manual, complex, and error-prone process. This paper introduces INDIANA, a comprehensive security verification methodology for hardware masking. Our results include a hardware verification tool, enabling a complete analysis of simulation-based security in the glitch-extended probing model and intra-cycle estimations for leakage probabilities in the random...

In this paper, we present a new efficient stand-alone MAC construct named SMAC, based on processing using the Finite State Machine (FSM) part of the stream cipher family SNOW, which in turn uses the AES round function. It offers a combination of very high speed in software and hardware with a truncatable tag. Three concrete base versions of SMAC are proposed, each offering a different security level. SMAC can also be directly integrated with an external ciphering engine in an AEAD mode....