While passive side-channel attacks and active fault attacks have been studied intensively in the last few decades, strong attackers combining these attacks have only been studied relatively recently. Due to its simplicity, most countermeasures against passive attacks are based on additive sharing. Unfortunately, extending these countermeasures against faults often leads to quite a significant performance penalty, either due to the use of expensive cryptographic operations or a large number...

Mathematically secured cryptographic implementations leak critical information in terms of power, EM emanations, etc. Several circuit-level countermeasures are proposed to hinder side channel leakage at the source. Circuit-level countermeasures (e.g., IVR, STELLAR, WDDL, etc) are often preferred as they are generic and have low overhead. They either dither the voltage randomly or attenuate the meaningful signature at $V_{DD}$ port. Although any digital implementation has two generic ports,...

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...

In this paper, we present a new efficient stand-alone MAC construct based on processing using the 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 versions of SMAC are proposed with different security levels, although other use cases are also possible. For example, SMAC can be combined with an external ciphering engine in AEAD mode. Every design...

In our highly digitalized world, an adversary is not constrained to purely digital attacks but can monitor or influence the physical execution environment of a target computing device. Such side-channel or fault-injection analysis poses a significant threat to otherwise secure cryptographic implementations. Hence, it is important to consider additional adversarial capabilities when analyzing the security of cryptographic implementations besides the default black-box model. For side-channel...

Recent years have witnessed a significant development for functional encryption (FE) in the multi-user setting, particularly with multi-client functional encryption (MCFE). The challenge becomes more important when combined with access control, such as attribute-based encryption (ABE), which was actually not covered by the FE and MCFE frameworks. On the other hand, as for complex primitives, many works have studied the admissibility of adversaries to ensure that the security model...

This work proposes a new white-box attack technique called filtering, which can be combined with any other trace-based attack method. The idea is to filter the traces based on the value of an intermediate variable in the implementation, aiming to fix a share of a sensitive value and degrade the security of an involved masking scheme. Coupled with LDA (filtered LDA, FLDA), it leads to an attack defeating the state-of-the-art SEL masking scheme (CHES 2021) of arbitrary degree and number of...

Let $\star: G \times X \rightarrow X$ be the action of a group $G$ of size $N=|G|$ on a set $X$. Let $y = g \star x \in X$ be a group action dlog instance, where our goal is to compute the unknown group element $g \in G$ from the known set elements $x,y \in X$. The Galbraith-Hess-Smart (GHS) collision finding algorithm solves the group action dlog in $N^{\frac 1 2}$ steps with polynomial memory. We show that group action dlogs are suitable for precomputation attacks. More...

As we enter 2024, the post-quantum cryptographic algorithm Dilithium, which emerged from the National Institute of Standards and Technology post-quantum cryptography competition, has now reached the deployment stage. This paper focuses on the practical security of Dilithium. We performed practical attacks on Dilithium2 on an STM32F4 platform. Our results indicate that an attack can be executed with just two signatures within five minutes, with a single signature offering a 60% probability of...

This paper presents SNOW-SCA, the first power side-channel analysis (SCA) attack of a 5G mobile communication security standard candidate, SNOW-V, running on a 32-bit ARM Cortex-M4 microcontroller. First, we perform a generic known-key correlation (KKC) analysis to identify the leakage points. Next, a correlation power analysis (CPA) attack is performed, which reduces the attack complexity to two key guesses for each key byte. The correct secret key is then uniquely identified utilizing...

Physical security is an important aspect of devices for which an adversary can manipulate the physical execution environment. Recently, more and more attention has been directed towards a security model that combines the capabilities of passive and active physical attacks, i.e., an adversary that performs fault-injection and side-channel analysis at the same time. Implementing countermeasures against such a powerful adversary is not only costly but also requires the skillful combination of...

In this paper, we present a new type of algebraic attack that applies to many recent arithmetization-oriented families of permutations, such as those used in Griffin, Anemoi, ArionHash, and XHash8, whose security relies on the hardness of the constrained-input constrained-output (CICO) problem. We introduce the FreeLunch approach: the monomial ordering is chosen so that the natural polynomial system encoding the CICO problem already is a Gröbner basis. In addition, we present a new dedicated...

Physical attacks pose a substantial threat to the secure implementation of cryptographic algorithms. While considerable research efforts are dedicated to protecting against passive physical attacks (e.g., side-channel analysis (SCA)), the landscape of protection against other types of physical attacks remains a challenge. Fault attacks (FA), though attracting growing attention in research, still lack the prevalence of provably secure designs when compared to SCA. The realm of combined...

Recently the notion of blockwise error in a context of rank based cryptography has been introduced by Sont et al. at AsiaCrypt 2023 . This notion of error, very close to the notion sum-rank metric, permits, by decreasing the weight of the decoded error, to greatly improve parameters for the LRPC and RQC cryptographic schemes. A little before the multi-syndromes approach introduced for LRPC and RQC schemes had also allowed to considerably decrease parameters sizes for LRPC and RQC schemes,...

The partial sums cryptanalytic technique was introduced in 2000 by Ferguson et al., who used it to break 6-round AES with time complexity of $2^{52}$ S-box computations -- a record that has not been beaten ever since. In 2014, Todo and Aoki showed that for 6-round AES, partial sums can be replaced by a technique based on the Fast Fourier Transform (FFT), leading to an attack with a comparable complexity. In this paper we show that the partial sums technique can be combined with an...

Fault attacks impose a serious threat against the practical implementations of cryptographic algorithms. Statistical Ineffective Fault Attacks (SIFA), exploiting the dependency between the secret data and the fault propagation overcame many of the known countermeasures. Later, several countermeasures have been proposed to tackle this attack using error detection methods. However, the efficiency of the countermeasures, in part governed by the number of error checks, still remains a...

Quantum computers hold the potential to solve problems that are intractable for classical computers, thereby driving increased interest in the development of new cryptanalytic ciphers. In NIST's post-quantum standardization process, the security categories are defined by the costs of quantum key search against AES. However, the cost estimates provided by Grassl et al. for the search are high. NIST has acknowledged that these initial classifications should be approached cautiously, since the...

Physical attacks are well-known threats to cryptographic implementations. While countermeasures against passive Side-Channel Analysis (SCA) and active Fault Injection Analysis (FIA) exist individually, protecting against their combination remains a significant challenge. A recent attempt at achieving joint security has been published at CCS 2022 under the name CINI-MINIS. The authors introduce relevant security notions and aim to construct arbitrary-order gadgets that remain trivially...

Real-world cryptographic implementations nowadays are not only attacked via classical cryptanalysis but also via implementation attacks, including passive attacks (observing side-channel information about the inner computation) and active attacks (inserting faults into the computation). While countermeasures exist for each type of attack, countermeasures against combined attacks have only been considered recently. Masking is a standard technique for protecting against passive side-channel...

Deploying cryptography on embedded systems requires security against physical attacks. At CHES 2019, M&M was proposed as a combined countermeasure applying masking against SCAs and information-theoretic MAC tags against FAs. In this paper, we show that one of the protected AES implementations in the M&M paper is vulnerable to a zero-value SIFA2-like attack. A practical attack is demonstrated on an ASIC board. We propose two versions of the attack: the first follows the SIFA approach to...

Incompressibility is a popular security notion for white-box cryptography and captures that a large encryption program cannot be compressed without losing functionality. Fouque, Karpman, Kirchner and Minaud (FKKM) defined strong incompressibility, where a compressed program should not even help to distinguish encryptions of two messages of equal length. Equivalently, the notion can be phrased as indistinguishability under chosen-plaintext attacks and key-leakage (LK-IND-CPA), where the...

This note shows that there exists a nontrivial invariant for the unkeyed round function of QARMAv2-64. It is invariant under translation by a set of $2^{32}$ constants. The invariant does not extend over all rounds of QARMAv2-64 and probably does not lead to full-round attacks. Nevertheless, it might be of interest as it can be expected to give meaningful weak-key attacks on round-reduced instances when combined with other techniques such as integral cryptanalysis.

Recently, Biryukov et al. presented a new technique for key recovery in differential cryptanalysis, called meet-in-the-filter (MiF). In this work, we develop theoretical and practical aspects of the technique, which helps understanding and simplifies application. In particular, we show bounds on MiF complexity and conditions when the MiF-enhanced attack may reach them. We present a method based on trail counting which allows to estimate filtering strength of involved rounds and perform...

Physically Unclonable Functions (PUFs) are being proposed as a low cost alternative to permanently store secret keys or provide device authentication without requiring non-volatile memory, large e-fuses or other dedicated processing steps. In the literature, PUFs are split into two main categories. The so-called strong PUFs are mainly used for authentication purposes, hence also called authentication PUFs. They promise to be lightweight by avoiding extensive digital post-processing and...

FPGA-SoCs are a popular platform for accelerating a wide range of applications due to their performance and flexibility. From a security point of view, these systems have been shown to be vulnerable to various attacks, especially side-channel attacks where an attacker can obtain the secret key of a cryptographic algorithm via laboratory mea- surement equipment or even remotely with sensors implemented inside the FPGA logic itself. Fortunately, a variety of countermeasures on...

MIBS is a 32-round lightweight block cipher following a Feistel structure with the block length of 64-bit and the key length of 64 or 80 bits. In this paper, the properties of the key scheduling algorithm are investigated and lots of repeated bits among the different round keys are found. Moreover, the optimal guessing order of the unknown key bits is obtained by using the greedy algorithm. At last, combined with the early abort technique, the differential cryptanalyses are improved to 15...

GIFT-64 is a block cipher that has received a lot of attention from the community since its proposal in 2017. The attack on the highest number of rounds is a differential related-key attack on 26 rounds~\cite{DBLP:journals/tosc/SunWW21}. We studied this attack, in particular with respect to the generic framework for improving key recovery from~\cite{DBLP:conf/asiacrypt/BrollCFLN21}, and we realised that this framework, combined with an efficient parallel key guessing of interesting subsets...

The recent work of Chaturvedi et al. (ePrint 2022/685) claims to observe leakage about secret information in a ciphertext of TFHE through a timing side-channel on the (untrusted) server. In (Chaturvedi et al., ePrint 2022/1563) this is combined with an active attack against TFHE and FHEW. The claims in (Chaturvedi et al., ePrint 2022/685) about the non-trivial leakage from a ciphertext would have far-reaching implications, since the server does not have any secret inputs. In particular, this...

In the seminal work published by Gohr in CRYPTO 2019, neural networks were successfully exploited to perform differential attacks on Speck32/64, the smallest member in the block cipher family Speck. The deep learning aided key-recovery attack by Gohr achieves considerable improvement in terms of time complexity upon the state-of-the-art result from the conventional cryptanalysis method. A further question is whether the advantage of deep learning aided attacks can be kept on large-state...

FALCON and Crystals-Dilithium are the digital signatures algorithms selected as NIST PQC standards at the end of the third round. FALCON has the advantage of the shortest size of the combined public key and signature but has the disadvantage of the relatively long signing time. Since FALCON algorithm is faithfully designed based on theoretical security analysis, the implementation of the algorithms is quite complex and needs considerable complexity. In order to implement the FALCON...

An emerging direction of investigating the resilience of post-quantum cryptosystems under side-channel attacks is to consider the situations where leaked information is combined with traditional attack methods in various forms. In CRYPTO 2020, Dachman-Soled et al. integrated hints from side-channel information to the primal attack against LWE schemes. This idea is further developed in this paper. An accurate characterization of the information from perfect hints and modular hints is obtained...

Post-quantum signature schemes based on the MPC-in-the-Head (MPCitH) paradigm are recently attracting significant attention as their security solely depends on the one-wayness of the underlying primitive, providing diversity for the hardness assumption in post-quantum cryptography. Recent MPCitH-friendly ciphers have been designed using simple algebraic S-boxes operating on a large field in order to improve the performance of the resulting signature schemes. Due to their simple algebraic...

The Distorted Bounded Distance Decoding Problem (DBDD) was introduced by Dachman-Soled et al. [Crypto ’20] as an intermediate problem between LWE and unique-SVP (uSVP). They presented an approach that reduces an LWE instance to a DBDD instance, integrates side information (or “hints”) into the DBDD instance, and finally reduces it to a uSVP instance, which can be solved via lattice reduction. They showed that this principled approach can lead to algorithms for side-channel attacks that...

In ASIACRYPT 2017, Rønjom et al. analyzed AES with yoyo attack. Inspired by their 4-round AES distinguisher, Grassi proposed the mixture differential cryptanalysis as well as a key recovery attack on 5-round AES, which was shown to be better than the classical square attack in computation complexity. After that, Bardeh et al. combined the exchange attack with the 4-round mixture differential distinguisher of AES, leading to the first secret-key chosen plaintext distinguisher for 6-round...

Observation and manipulation of physical characteristics are well-known and powerful threats to cryptographic devices. While countermeasures against passive side-channel and active fault-injection attacks are well understood individually, combined attacks, i.e., the combination of fault injection and side-channel analysis, is a mostly unexplored area. Naturally, the complexity of analysis and secure construction increases with the sophistication of the adversary, making the combined scenario...

Even today, SCA attacks pose a serious threat to the security of cryptographic implementations fabricated with low-power and nano-scale feature technologies. Fortunately, the masking countermeasures offer reliable protection against such attacks based on simple security assumptions. However, the practical application of masking to a cryptographic algorithm is not trivial, and the designer may overlook possible security flaws, especially when masking a complex circuit. Moreover, abstract...

Secure multiparty computation (MPC) has been proposed to allow multiple mutually distrustful data owners to jointly train machine learning (ML) models on their combined data. However, by design, MPC protocols faithfully compute the training functionality, which the adversarial ML community has shown to leak private information and can be tampered with in poisoning attacks. In this work, we argue that model ensembles, implemented in our framework called SafeNet, are a highly MPC-amenable way...

Physical attacks, including passive Side-Channel Analysis and active Fault Injection Analysis, are considered among the most powerful threats against physical cryptographic implementations. These attacks are well known and research provides many specialized countermeasures to protect cryptographic implementations against them. Still, only a limited number of combined countermeasures, i.e., countermeasures that protect implementations against multiple attacks simultaneously, were proposed in...

In this work, we study and formalize security notions for algorithm substitution attacks (ASAs) on em cryptographic puzzles. Puzzles are difficult problems that require an investment of computation, memory, or some other related resource. They are heavily used as a building block for the consensus networks used by cryptocurrencies. These include primitives such as proof-of-work, proof-of-space, and verifiable delay functions (VDFs). Due to economies of scale, these networks increasingly rely...

Resource-based consensus is the backbone of permissionless distributed ledger systems. The security of such protocols relies fundamentally on the level of resources actively engaged in the system. The variety of different resources (and related proof protocols, some times referred to as PoX in the literature) raises the fundamental question whether it is possible to utilize many of them in tandem and build multi-resource consensus protocols. The challenge in combining different resources is...

In order to provide benefits in the areas of fully homomorphic encryption (FHE), multi-party computation (MPC), post-quantum signature schemes, or efficient masked implementations for side-channel resistance, reducing the number of multiplications has become a quite popular trend for the symmetric cryptographic primitive designs. With an aggressive design strategy exploiting the extremely simple and low-degree S-box and low number of rounds, Pyjamask, the fundamental block cipher of the AEAD...

Cryptanalysis of the LowMC block cipher when the attacker has access to a single known plaintext/ciphertext pair is a mathematically challenging problem. This is because the attacker is unable to employ most of the standard techniques in symmetric cryptography like linear and differential cryptanalysis. This scenario is particularly relevant while arguing the security of the \picnic digital signature scheme in which the plaintext/ciphertext pair generated by the LowMC block cipher serves as...

We introduce lattice-based practical seed-recovery attacks against two efficient number-theoretic pseudo-random number generators: the fast knapsack generator and a family of combined multiple recursive generators. The fast knapsack generator was introduced in 2009 by Von Zur Gathen and Shparlinski. It generates pseudo-random numbers very efficiently with strong mathematical guarantees on their statistical properties but its resistance to cryptanalysis was left open since 2009. The given...

We introduce the Clockwork Finance Framework (CFF), a general purpose, formal verification framework for mechanized reasoning about the economic security properties of composed decentralized-finance (DeFi) smart contracts. CFF features three key properties. It is contract complete, meaning that it can model any smart contract platform and all its contracts—Turing complete or otherwise. It does so with asymptotically constant model overhead. It is also attack-exhaustive by construction,...

We revisit the popular adage that side-channel countermeasures must be combined to be efficient, and study its application to bitslice masking and shuffling. Our contributions are threefold. First, we improve this combination: by shuffling the shares of a masked implementation rather than its tuples, we can amplify the impact of the shuffling exponentially in the number of shares, while this impact was independent of the masking security order in previous works. Second, we evaluate the...

Post-quantum cryptography (PQC) is nowadays a very active research field [1]. We follow a non-standard way to achieve it, taking any common protocol and replacing arithmetic with GF(2^8) field operations, a procedure defined as R-Propping [2-7]. The resulting protocol security relies on the intractability of a generalized discrete log problem, combined with the power sets of algebraic ring extension tensors and resilience to quantum and algebraic attacks. Oblivious Transfer (OT) is a...

The existence of one-way functions implies secure digital signatures, but not public-key encryption (at least in a black-box setting). Somewhat surprisingly, though, efficient public-key encryption schemes appear to be much easier to construct from concrete algebraic assumptions (such as the factoring of Diffie-Hellman-like assumptions) than efficient digital signature schemes. In this work, we provide one reason for this apparent difficulty to construct efficient signature...

Statistical Ineffective Fault Attacks (SIFA) have been recently proposed as very powerful key-recovery strategies on symmetric cryptographic primitives' implementations. Specically, they have been shown to bypass many common countermeasures against faults such as redundancy or infection, and to remain applicable even when side-channel countermeasures are deployed. In this work, we investigate combined side-channel and fault attacks and show that a profiled, SIFA-like attack can be applied...

Due to its amazing speed and multiplicative properties the Legendre PRF recently finds widespread applications e.g. in Ethereum 2.0, multiparty computation and in the quantum-secure signature proposal LegRoast. However, its security is not yet extensively studied. The Legendre PRF computes for a key $k$ on input $x$ the Legendre symbol $L_k(x) = \left( \frac {x k} {p} \right)$ in some finite field $\F_p$. As standard notion, PRF security is analysed by giving an attacker oracle access to...

Rasta and Dasta are two fully homomorphic encryption friendly symmetric-key primitives proposed at CRYPTO 2018 and ToSC 2020, respectively. We point out that the designers of Rasta and Dasta neglected an important property of the $\chi$ operation. Combined with the special structure of Rasta and Dasta, this property directly leads to significantly improved algebraic cryptanalysis. Especially, it enables us to theoretically break 2 out of 3 instances of full Agrasta, which is the aggressive...

An algebraic differential fault attack (ADFA) is an attack in which an attacker combines a differential fault attack and an algebraic technique to break a targeted cipher. In this paper, we present three attacks using three different algebraic techniques combined with a differential fault attack in the bit-flip fault model to break the SIMON block cipher. First, we introduce a new analytic method that is based on a differential trail between the correct and faulty ciphertexts. This method is...

We study post-quantum zero-knowledge (classical) protocols that are sound against quantum resetting attacks. Our model is inspired by the classical model of resetting provers (Barak-Goldreich-Goldwasser-Lindell, FOCS `01), providing a malicious efficient prover with oracle access to the verifier's next-message-function, fixed to some initial random tape; thereby allowing it to effectively reset (or equivalently, rewind) the verifier. In our model, the prover has quantum access to the...

Post-quantum cryptography or PQC is a trend that has a deserved NIST status, and which aims to be resistant to quantum computer attacks like Shor and Grover algorithms. We choose to follow a non-standard way to achieve PQC: taking any standard asymmetric protocol and replacing numeric field arithmetic with GF-256 field operations. By doing so, it is easy to implement R-propped asymmetric systems as present and former papers show. Here R stands for Rijndael as we work over the AES field. This...

In this paper, we present a new technique which can be used to find better linear approximations in ARX ciphers. Using this technique, we present the first explicitly derived linear approximations for 3 and 4 rounds of ChaCha and, as a consequence, it enables us to improve the recent attacks against ChaCha. Additionally, we present new differentials for 3 and 3.5 rounds of ChaCha that, when combined with the proposed technique, lead to further improvement in the complexity of the...

Various Artificial Intelligence (AI) techniques are combined with classic side-channel methods to improve the efficiency of attacks. Among them, Genetic Algorithms based Correlation Power Analysis (GA-CPA) is proposed to launch attacks on hardware cryptosystems to extract the secret key efficiently. However, the convergence rate is unsatisfactory due to two problems: individuals of the initial population generally have low fitnesses, and the mutation operation is hard to generate...

The progress on constructing quantum computers and the ongoing standardization of post-quantum cryptography (PQC) have led to the development and refinement of promising new digital signature schemes and key encapsulation mechanisms (KEM). Especially lattice-based schemes have gained some popularity in the research community, presumably due to acceptable key, ciphertext, and signature sizes as well as good performance results and cryptographic strength. However, in some practical...

Secure computation protocols enable mutually distrusting parties to compute a function of their private inputs while revealing nothing but the output. Protocols with {\em full security} (also known as {\em guaranteed output delivery}) in particular protect against denial-of-service attacks, guaranteeing that honest parties receive a correct output. This feature can be realized in the presence of an honest majority, and significant research effort has gone toward attaining full security with...

High-assurance cryptography leverages methods from program verification and cryptography engineering to deliver efficient cryptographic software with machine-checked proofs of memory safety, functional correctness, provable security, and absence of timing leaks. Traditionally, these guarantees are established under a sequential execution semantics. However, this semantics is not aligned with the behavior of modern processors that make use of speculative execution to improve performance....

Strong Physical Unclonable Functions (PUFs), as a promising security primitive, are supposed to be a lightweight alternative to classical cryptography for purposes such as device authentication. Most of the proposed candidates, however, have been plagued by machine-learning attacks breaking their security claims. The Interpose PUF (iPUF), which has been introduced at CHES 2019, was explicitly designed with state-of-the-art machine-learning attacks in mind and is supposed to be impossible to...

We present an algorithm solving the ROS (Random inhomogeneities in a Overdetermined Solvable system of linear equations) problem in polynomial time for l > log p dimensions. Our algorithm can be combined with Wagner’s attack, and leads to a sub-exponential solution for any dimension l with best complexity known so far. When concurrent executions are allowed, our algorithm leads to practical attacks against unforgeability of blind signature schemes such as Schnorr and Okamoto--Schnorr blind...

Recently introduced federated learning is an attractive framework for the distributed training of deep learning models with thousands of participants. However, it can potentially be used with malicious intent. For example, adversaries can use their smartphones to jointly train a classifier for extracting secret keys from the smartphones' SIM cards without sharing their side-channel measurements with each other. With federated learning, each participant might be able to create a strong model...

Protection against Side-Channel (SCA) and Fault Attacks (FA) requires two classes of countermeasures to be simultaneously embedded in a cryptographic implementation. It has already been shown that a straightforward combination of SCA and FA countermeasures are vulnerable against FAs, such as Statistical Ineffective Fault Analysis (SIFA) and Fault Template Attacks (FTA). Consequently, new classes of countermeasures have been proposed which prevent against SIFA, and also includes masking for...

Performance in hardware has typically played a major role in differentiating among leading candidates in cryptographic standardization efforts. Winners of two past NIST cryptographic contests (Rijndael in case of AES and Keccak in case of SHA-3) were ranked consistently among the two fastest candidates when implemented using FPGAs and ASICs. Hardware implementations of cryptographic operations may quite easily outperform software implementations for at least a subset of major performance...

Side-channel analysis and fault-injection attacks are known as serious threats to cryptographic hardware implementations and the combined protection against both is currently an open line of research. A promising countermeasure with considerable implementation overhead appears to be a mix of first-order secure Threshold Implementations and linear Error-Correcting Codes. In this paper we employ for the first time the inherent structure of non-systematic codes as fault...

We report an important implementation vulnerability exploitable through physical attacks for message recovery in five lattice-based public-key encryption schemes (PKE) and Key Encapsulation Mechanisms (KEM) - NewHope, Kyber, Saber, Round5 and LAC that are currently competing in the second round of NIST's standardization process for post-quantum cryptography. The reported vulnerability exists in the message decoding function which is a fundamental kernel present in lattice-based PKE/KEMs and...

This paper provides a theoretical background for a new consensus model called Proof of Review (PoR), which extends Algorand’s blockchain consensus model and reproduces the human mechanism for analyzing reviews through analysis and reputation. Our protocol derives the trustworthiness of a participant’s reputation through a consensus of these reviews. In this new protocol, we combined concepts from proof of stake and proof of reputation to ensure a blockchain system comes to consensus on an...

We present a new multiparty protocol for the distributed generation of biprime RSA moduli, with security against any subset of maliciously colluding parties assuming oblivious transfer and the hardness of factoring. Our protocol is highly modular, and its uppermost layer can be viewed as a template that generalizes the structure of prior works and leads to a simpler security proof. We introduce a combined sampling-and-sieving technique that eliminates both the inherent leakage in the...

Recent works in side-channel analysis have been fully relying on training classification models to recover sensitive information from traces. However, the knowledge of an attacker or an evaluator is not taken into account and poorly capturedby solely training a classifier on signals. This paper proposes to inject prior information in preprocessing and classification in order to increase the performance of side-channel attacks (SCA). First wepropose to use the Wavelet Scattering Transform,...

This paper has four main goals. First, we show how we solved the CHES 2018 AES challenge in the contest using essentially a linear classifier combined with a SAT solver and a custom error correction method. This part of the paper has previously appeared in a preprint by the current authors (e-print report 2019/094) and later as a contribution to a preprint write-up of the solutions by the three winning teams (e-print report 2019/860). Second, we develop a novel deep neural network...

In the profiled side-channel analysis, deep learning-based techniques proved to be very successful even when attacking targets protected with countermeasures. Still, there is no guarantee that deep learning attacks will always succeed. Various countermeasures make attacks significantly more complicated, and those countermeasures can be further combined to make the attacks even more challenging. An intuitive solution to improve the performance of attacks would be to reduce the effect of...

Recent results have shown that some post-quantum cryptographic systems have encryption and decryption performance comparable to fast elliptic-curve cryptography (ECC) or even better. However, this performance metric is considering only CPU time and ignoring bandwidth and storage. High-confidence post-quantum encryption systems have much larger keys than ECC. For example, the code-based cryptosystem recommended by the PQCRYPTO project uses public keys of 1MB. Fast key erasure (to provide...

Historically, fault diagnosis for integrated circuits has singularly dealt with reliability concerns. In contrast, a cryptographic circuit needs to be primarily evaluated concerning information leakage in the presence of maliciously crafted faults. While Differential Fault Attacks (DFAs) on symmetric ciphers have been known for over 20 years, recent developments have tried to structurally classify the attackers’ capabilities as well as the properties of countermeasures. Correct realization...

In this paper, we initiate the study of side-channel leakage in hash-and-sign lattice-based signatures, with particular emphasis on the two efficient implementations of the original GPV lattice-trapdoor paradigm for signatures, namely NIST second-round candidate Falcon and its simpler predecessor DLP. Both of these schemes implement the GPV signature scheme over NTRU lattices, achieving great speed-ups over the general lattice case. Our results are mainly threefold. First, we identify a...

Blockchain brings dawn to decentralized applications which coordinate correct computations without a prior trust. However, existing scalable on-chain frameworks are incompetent in dealing with intensive validation. On the one hand, duplicated execution pattern leads to limited throughput and unacceptable expenses. On the other hand, there lack fair and secure incentive mechanisms allocating rewards according to the actual workload of validators, thus deriving bad dilemmas among rational...

Boomerang attacks are extensions of differential attacks, that make it possible to combine two unrelated differential properties of the first and second part of a cryptosystem with probabilities $p$ and $q$ into a new differential-like property of the whole cryptosystem with probability $p^2q^2$ (since each one of the properties has to be satisfied twice). In this paper we describe a new version of boomerang attacks which uses the counterintuitive idea of throwing out most of the data...

The goal of white-box cryptography is to provide security even when the cryptographic implementation is executed in adversarially controlled environments. White-box implementations nowadays appear in commercial products such as mobile payment applications, e.g., those certified by Mastercard. Interestingly, there, white-box cryptography is championed as a tool for secure storage of payment tokens, and importantly, the white-boxed storage functionality is bound to a hardware functionality to...

In different contexts such as filtered LFSR, Goldreich's PRG, and FLIP stream ciphers, the security of a cryptographic primitive mostly depends on the algebraic properties of one Boolean function. Since the Seventies, more and more efficient attacks have been exhibited in this context, related to more and more general algebraic properties, such as the degree, the algebraic immunity, and finally, the fast algebraic immunity. Once the properties to estimate the attack complexities are...

Fault attacks (FA) intentionally inject some fault into the encryption process for analyzing a secret key based on faulty intermediate values or faulty ciphertexts. One of the easy ways for software-based countermeasures is to use time redundancy. However, existing methods can be broken by skipping comparison operations or by using non-uniform distributions of faulty intermediate values. In this paper, we propose a secure software-based redundancy, aptly named table redundancy, applying...

In side-channel analysis attacks, on-die localized EM monitoring enable high bandwidth measurements of only a relevant part of the Integrated Circuit (IC). This can lead to improved attacks compared to cases where only power consumption is measured. Combined with profiled attacks which utilize a training phase to create precise models of the information leakage, the attacks can become even more powerful. In contrast, localized EM measurements can cause difficulties in applying the learned...

In this paper we give nearly tight reductions for modern implicitly authenticated Diffie-Hellman protocols in the style of the Signal and Noise protocols, which are extremely simple and efficient. Unlike previous approaches, the combination of nearly tight proofs and efficient protocols enables the first real-world instantiations for which the parameters can be chosen in a theoretically sound manner, i.e., according to the bounds of the reductions. Specifically, our reductions have a...

Several combined attacks have shown promising results in recovering cryptographic keys by introducing collision information into divide-and-conquer attacks to transform a part of the best key candidates within given thresholds into a much smaller collision space. However, these Collision-Optimized Divide-and-Conquer Attacks (CODCAs) uniformly demarcate the thresholds for all sub-keys, which is unreasonable. Moreover, the inadequate exploitation of collision information and backward fault...

Current blockchains are restricted by the low throughput. Aimed at this problem, we propose Txilm, a protocol that compresses the size of transaction presentation in each block and thus saves the bandwidth of the blockchain network. In this protocol, a block carries short hashes of TXIDs instead of complete transactions. Combined with the transaction list sorted by TXIDs, Txilm realizes 80 times of data size reduction compared with the original blockchains. We also evaluate the probability...

Differential Power Analysis and Differential Fault Analysis threaten the security of even the most trustworthy cryptographic primitives. It is important we protect their implementation such that no sensitive information is leaked using side channels and it withstands injected faults or combined physical attacks. In this work, we propose security notions tailored against advanced physical attacks consisting of both faults and probes on circuit wires. We then transform the security notions to...

Right from its introduction by Boneh et al., fault attacks (FA) have been established to be one of the most practical threats to both public key and symmetric key based cryptosystems. Statistical Ineffective Fault Analysis (SIFA) is a recently proposed class of fault attacks introduced at CHES 2018. The fascinating feature of this attack is that it exploits the correct ciphertexts obtained during a fault injection campaign, instead of the faulty ciphertexts. The SIFA has been shown to bypass...

Ensuring secure deduplication of encrypted data is a very active topic of research because deduplication is effective at reducing storage costs. Schemes supporting deduplication of encrypted data that are not vulnerable to content guessing attacks (such as Message Locked Encryption) have been proposed recently [Bellare et al. 2013, Li et al. 2015]. However in all these schemes, there is a key derivation phase that solely depends on a short hash of the data and not the data itself....

Lattice-based public-key encryption has a large number of design choices that can be combined in diverse ways to obtain different tradeoffs. One of these choices is the distribution from which secret keys are sampled. Numerous secret-key distributions exist in the state of the art, including (discrete) Gaussian, binomial, ternary, and fixed-weight ternary. Although the secret-key distribution impacts both the concrete security and the performance of the schemes, it has not been compared in a...

Second-order analyses have shown a great interest to defeat first level of masking protections. Their practical realization remains tedious in a lot of cases. This is partly due to the difficulties of achieving a fine alignment of two areas that are combined together afterward. Classical protections makes therefore use of random jitter or shuffling to make the alignment difficult or even impossible. This paper extends Scatter attack to high-order analyses. Processing the jointdistribution of...

In the implicit certification model, the process of verifying the validity of the signer's public key is combined with the verification of the signature itself. When compared to traditional, explicit certificates, the main advantage of the implicit approach lies in the shorter public key validation data. This property is particularly important in resource-constrained scenarios where public key validation is performed very often, which is common in vehicular communications (V2X) that employ...

A typical countermeasure against side-channel attacks consists of masking intermediate values with a random number. In symmetric cryptographic algorithms, Boolean shares of the secret are typically used, whereas in asymmetric algorithms the secret exponent/scalar is typically masked using algebraic properties. This paper presents a new exponent splitting technique with minimal impact on performance based on Boolean shares. More precisely, it is shown how an exponent can be efficiently split...

Cryptographic implementations on embedded systems need to be protected against physical attacks. Today, this means that apart from incorporating countermeasures against side-channel analysis, implementations must also withstand fault attacks and combined attacks. Recent proposals in this area have shown that there is a big tradeoff between the implementation cost and the strength of the adversary model. In this work, we introduce a new combined countermeasure M&M that combines Masking with...

At Crypto 2016, Kaplan et al. proposed the first quantum exponential acceleration of a classical symmetric cryptanalysis technique: they showed that, in the superposition query model, Simon's algorithm could be applied to accelerate the slide attack on the alternate-key cipher. This allows to recover an n-bit key with O(n) quantum time and queries. In this paper we propose many other types of quantum slide attacks. First, we are able to quantize classical advanced slide attacks on Feistel...

We consider the problem of Non-Interactive Secure Computation (NISC), a 2-message ``Sender-Receiver'' secure computation protocol that retains its security even when both parties can be malicious. While such protocols are easy to construct using garbled circuits and general non-interactive zero-knowledge proofs, this approach inherently makes a non-black-box use of the underlying cryptographic primitives and is infeasible in practice. Ishai et al. (Eurocrypt 2011) showed how to construct...

The recent lattice-based signature scheme Dilithium, submitted as part of the CRYSTALS (Cryptographic Suite for Algebraic Lattices) package, is one of a number of strong candidates submitted for the NIST standardisation process of post-quantum cryptography. The Dilithium signature scheme is based on the Fiat-Shamir paradigm and can be seen as a variant of the Bai-Galbraith scheme (BG) combined with several improvements from previous ancestor lattice-based schemes like GLP and BLISS signature...

Standardization bodies such as NIST and ETSI are currently seeking quantum resistant alternatives to vulnerable RSA and elliptic curve-based public-key algorithms. In this context, we present Round5, a lattice-based cryptosystem providing a key encapsulation mechanism and a public-key encryption scheme. Round5 is based on the General Learning with Rounding problem, unifying non-ring and ring lattice rounding problems into one. Usage of rounding combined with a tight analysis leads to...

The CCA-secure lattice-based post-quantum key encapsulation scheme Saber is a candidate in the NIST's post-quantum cryptography standardization process. In this paper, we study the implementation aspects of Saber in resource-constrained microcontrollers from the ARM Cortex-M series which are very popular for realizing IoT applications. In this work, we carefully optimize various parts of Saber for speed and memory. We exploit digital signal processing instructions and efficient memory access...

Dual receiver encryption (DRE), proposed by Diament et al. at ACM CCS 2004, is a special extension notion of public-key encryption, which enables two independent receivers to decrypt a ciphertext into a same plaintext. This primitive is quite useful in designing combined public key cryptosystems and denial of service attack-resilient protocols. Up till now, a series of DRE schemes are constructed from bilinear pairing groups and lattices. In this work, we introduce a construction of...

Post-quantum cryptography has drawn considerable attention from cryptologists on a global scale. At Asiacrypt 2017, Leander and May combined Grover's and Simon's quantum algorithms to break the FX-based block ciphers, which were introduced by Kilian and Rogaway to strengthen DES. In this study, we investigate the Feistel constructions using Grover's and Simon's algorithms to generate new quantum key-recovery attacks on different rounds of Feistel constructions. Our attacks require...

In this paper we introduce two things: On one hand we introduce the Tile-Probe-and-Fault model, a model generalising the wire-probe model of Ishai et al. extending it to cover both more realistic side-channel leakage scenarios on a chip and also to cover fault and combined attacks. Secondly we introduce CAPA: a combined Countermeasure Against Physical Attacks. Our countermeasure is motivated by our model, and aims to provide security against higher-order SCA, multiple-shot FA and combined...

Logic encryption is a hardware security technique that uses extra key inputs to prevent unauthorized use of a circuit. With the discovery of the SAT-based attack, new encryption techniques such as SARLock and Anti-SAT are proposed, and further combined with traditional logic encryption techniques, to guarantee both high error rates and resilience to the SAT-based attack. In this paper, the SAT-based bit-flipping attack is presented. It first separates the two groups of keys via SAT-based...

We present the first practically realizable side-channel assisted fault attack on PRESENT, that can retrieve the last round key efficiently using single nibble faults. The attack demonstrates how side-channel leakage can allow the adversary to precisely determine the fault mask resulting from a nibble fault injection instance. We first demonstrate the viability of such an attack model via side-channel analysis experiments on top of a laser-based fault injection setup, targeting a PRESENT-80...