The impossible differential (ID) attack is crucial for analyzing the strength of block ciphers. The critical aspect of this technique is to identify IDs, and the researchers introduced several methods to detect them. Recently, the researchers extended the mixed-integer linear programming (MILP) approach by partitioning the input and output differences to identify IDs. The researchers proposed techniques to determine the representative set and partition table of a set over any nonlinear...

In this work, we introduce ToFA, the first fault attack (FA) strategy that attempts to leverage the classically well-known idea of impossible differential cryptanalysis to mount practically verifiable attacks on bit-oriented ciphers like GIFT and BAKSHEESH. The idea used stems from the fact that truncated differential paths induced due to fault injection in certain intermediate rounds of the ciphers lead to active SBox-es in subsequent rounds whose inputs admit specific truncated...

BAKSHEESH is a lightweight block cipher following up the well-known cipher GIFT-128, which uses a 4-bit SBox that has a non-trivial Linear Structure (LS). Also, the Sbox requires a low number of AND gates that makes BAKSHEESH stronger to resist the side channel attacks compared to GIFT-128. In this paper, we give the first third-party security analysis of BAKSHEESH from the traditional attacks perspective: integral, differential and linear attacks. Firstly, we propose a framework for...

The analytical perspective employed in the study classifies the theoretical research on dependencies in differential characteristics into two types. By categorising all dependence representations from the value restrictions and the theory of quasidifferential trails, we pinpoint a specific set of nonlinear constraints, which we term linearised nonlinear constraints. We aim to establish a method that utilises value restrictions to identify these constraints, as the current method based on...

In recent years, ML based differential distinguishers have been explored and compared with the classical methods. Complexity of a key recovery attack on block ciphers is calculated using the probability of a differential distinguisher provided by classical methods. Since theoretical computations suffice to calculate the data complexity in these cases, so there seems no restrictions on the practical availability of computational resources to attack a block cipher using classical methods....

In this work, we take a look at the two recently proposed block ciphers, DEFAULT and BAKSHEESH, both of which are descendent of another block cipher named GIFT. We show that both ciphers can be interpreted within the partial non-linear layer category, thanks to the SBoxes having at least one non-trivial linear structure. We also reevaluate the security claim of DEFAULT.

In recent years, quantum technology has been rapidly developed. As security analyses for symmetric ciphers continue to emerge, many require an evaluation of the resources needed for the quantum circuit implementation of the encryption algorithm. In this regard, we propose the quantum circuit decision problem, which requires us to determine whether there exists a quantum circuit for a given permutation f using M ancilla qubits and no more than K quantum gates within the circuit depth D....

Differential cryptanalysis is an old and powerful attack against block ciphers. While different techniques have been introduced throughout the years to improve the complexity of this attack, the key recovery phase remains a tedious and error-prone procedure. In this work, we propose a new algorithm and its associated tool that permits, given a distinguisher, to output an efficient key guessing strategy. Our tool can be applied to SPN ciphers whose linear layer consists of a bit-permutation...

In some linear key recovery attacks, the function which determines the value of the linear approximation from the plaintext, ciphertext and key is replaced by a similar map in order to improve the time or memory complexity at the cost of a data complexity increase. We propose a general framework for key recovery map substitution, and introduce Walsh spectrum puncturing, which consists of removing carefully-chosen coefficients from the Walsh spectrum of this map. The capabilities of this...

In this paper, inspired by the work of Beyne and Rijmen at CRYPTO 2022, we explore the accurate probability of $d$-differential in the fixed-key model. The theoretical foundations of our method are based on a special matrix $-$ quasi-$d$-differential transition matrix, which is a natural extension of the quasidifferential transition matrix. The role of quasi-$d$-differential transition matrices in polytopic cryptananlysis is analogous to that of correlation matrices in linear cryptanalysis....

GIFT is a family of lightweight block ciphers based on SPN structure and composed of two versions named GIFT-64 and GIFT-128. In this paper, we reevaluate the security of GIFT-64 against the rectangle attack under the related-key setting. Investigating the previous rectangle key recovery attack on GIFT-64, we obtain the core idea of improving the attack——trading off the time complexity of each attack phase. We flexibly guess part of the involved subkey bits to balance the time cost of each...

The substitution box (S-box) is an important nonlinear component in most symmetric cryptosystems and thus should have good properties. Its difference distribution table (DDT) and linear approximation table (LAT) affect the security of the cipher against differential and linear cryptanalysis. In most previous work, differential uniformity and linearity of an S-box are two primary cryptographic properties to impact the resistance against differential and linear attacks. In some cases, the...

We propose a lightweight block cipher named BAKSHEESH, which follows up on the popular cipher GIFT-128 (CHES'17). BAKSHEESH runs for 35 rounds, which is 12.50 percent smaller compared to GIFT-128 (runs for 40 rounds) while maintaining the same security claims against the classical attacks. The crux of BAKSHEESH is to use a 4-bit SBox that has a non-trivial Linear Structure (LS). An SBox with one or more non-trivial LS has not been used in a cipher construction until DEFAULT...

In the design of GIFT, half round key XOR is used. This leads to the undesired consequence that the security against the differential/linear attacks are overestimated. This comes from the observation that; in the usual DDT/LAT based analysis of the differential/linear attacks, the inherent assumption is the full round key is XORed at each round.

The division property introduced by Todo in Crypto 2015 is one of the most versatile tools in the arsenal of a cryptanalyst which has given new insights into many ciphers primarily from an algebraic perspective. On the other end of the spectrum we have fault attacks which have evolved into the deadliest of all physical attacks on cryptosystems. The current work aims to combine these seemingly distant tools to come up with a new type of fault attack. We show how fault invariants are formed...

With the escalating demand for lightweight ciphers as well as side channel protected implementation of those ciphers in recent times, this work focuses on two related aspects. First, we present a tool for automating the task of finding a Threshold Implementation (TI) of a given Substitution Box (SBox). Our tool returns `with decomposition' and `without decomposition' based TI. The `with decomposition' based implementation returns a combinational SBox; whereas we get a sequential SBox from...

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...

Impossible differential (ID) cryptanalysis is one of the most important cryptanalytic approaches for block ciphers. How to evaluate the security of Substitution-Permutation Network (SPN) block ciphers against ID is a valuable problem. In this paper, a series of methods for bounding the length of IDs of SPN block ciphers are proposed. From the perspective of overall structure, we propose a general framework and three implementation strategies. The three implementation strategies are compared...

Cryptanalysts have been looking for differential characteristics in ciphers for decades and it remains unclear how the subkey values and more generally the Markov assumption impacts exactly their probability estimation. There were theoretical efforts considering some simple linear relationships between differential characteristics and subkey values, but the community has not yet explored many possible nonlinear dependencies one can find in differential characteristics. Meanwhile, the...

The NIST LightWeight Cryptography (LWC) selection process aims to standardise cryptographic functionality which is suitable for resource-constrained devices. Since the outcome is likely to have significant, long-lived impact, careful evaluation of each submission with respect to metrics explicitly outlined in the call is imperative. Beyond the robustness of submissions against cryptanalytic attack, metrics related to their implementation (e.g., execution latency and memory footprint) form an...

Lightweight cryptography is a viable solution for constrained computational environments that require a secure communication channel. To standardize lightweight primitives, NIST has published a call for algorithms that address needs like compactness, low-latency, low-power/energy, etc. Among the candidates, the GIFT family of block ciphers was utilized in various NIST candidates due to its high-security margin and small gate footprint. As a result of their hardware-oriented design, software...

The GIFT-64-128 block cipher encryption is implemented in MIPS assembly language. The program is assembled and simulated using the QtSPIM simu-lator and produces functionally correct results. This implementation requires 22,764 clock cycles per 64-bit block encryption, as well as 1,296 bytes of code, and 192 bytes of data memory. The major functional units of the im-plementation are analyzed in terms of cycle count and bytes of code.

Impossible differential (ID) cryptanalysis is one of the most important attacks on block ciphers. The Mixed Integer Linear Programming (MILP) model is a popular method to determine whether a specific difference pair is an ID. Unfortunately, due to the huge search space (approximately $2^{2n}$ for a cipher with a block size $n$ bits), we cannot leverage this technique to exhaust all difference pairs, which is a well-known long-standing problem. In this paper, we propose a systematic...

We analyze nonce-misuse resilience (NMRL) security of Romulus-N and GIFT-COFB, the two finalists of NIST Lightweight Cryptography project for standardizing lightweight authenticated encryption. NMRL, introduced by Ashur et al. at CRYPTO 2017, is a relaxed security notion from a stronger, nonce-misuse resistance notion. We proved that Romulus-N and GIFT-COFB have nonce-misuse resilience. For Romulus-N, we showed the perfect privacy (NMRL-PRIV) and n/2-bit authenticity (NMRL-AUTH) with...

GIFT-COFB is a lightweight AEAD scheme and a submission to the ongoing NIST lightweight cryptography standardization process where it currently competes as a finalist. The construction processes 128-bit blocks with a key and nonce of the same size and has a small register footprint, only requiring a single additional 64-bit register. Be- sides the block cipher, the mode of operation uses a bit permutation and finite field multiplication with different constants. It is a well-known...

One of the main challenges cryptography needs to deal with is balancing the performances of a cryptographic primitive with its security. That is why in 2015, the National Institute of Standards and Technologies (NIST) has begun a standardization process to solicit the creation of new lightweight cryptographic algorithms. We then wondered which of this standardization finalists would suit the best to a white-box implementation. To this end, we studied different algorithms structures on...

Division property is an effective method for finding integral distinguishers for block ciphers, performing cube attacks on stream ciphers, and studying the algebraic degree of boolean functions. One of the main problems in this field is how to provably find the smallest input multiset leading to a balanced output. In this paper, we propose a new method based on division property for finding integral distinguishers with a provably minimum data complexity on permutation functions and block...

In this paper, we focus on constructing an automatic search model that greatly improves efficiency with little loss of accuracy and obtains some better results in the construction of integral distinguishers for block ciphers. First, we define a new notion named BDPT Trail, which divides BDPT propagation into three parts: the division trail for K, division trail for L, and Key-Xor operation. Secondly, we improve the insufficiency of the previous methods of calculating division trails and...

In this study, we accelerate Matsui's search algorithm to search for the best differential and linear trails of AES-like ciphers. Our acceleration points are twofold. The first exploits the structure and branch number of an AES-like round function to apply strict pruning conditions to Matsui's search algorithm. The second employs permutation characteristics in trail search to reduce the inputs that need to be analyzed. We demonstrate the optimization of the search algorithm by obtaining the...

Differential attack is a basic cryptanalysis method for block ciphers that exploits the high probability relations between the input and output differences. The existing work in quantum differential cryptanalysis of block ciphers focuses on resource estimation to recover the last round subkeys on the basis of existing relations constructed on classical computers. To find such relations using quantum computer, we propose a method to search the high probability differential and impossible...

GIFT-64 is a 64-bit block cipher with a 128-bit key that is more lightweight than PRESENT. This paper provides a detailed analysis of GIFT-64 against differential and linear attacks. Our work complements automatic search methods for the best differential and linear characteristics with a careful manual analysis. This hybrid approach leads to new insights. In the differential setting, we theoretically explain the existence of differential characteristics with two active S-boxes per round and...

In ToSC 2021(2), Sun et al. implemented an automatic search with the Boolean satisfiability problem (SAT) method on GIFT-128 and identified a 19-round linear approximation with the expected linear potential being $2^{-117.43}$, which is utilised to launch a 24-round attack on the cipher. In this addendum, we discover a new 19-round linear approximation with a lower expected linear potential. However, in the attack, one more round can be appended after the distinguisher. As a result, we...

We study the provable security claims of two NIST Lightweight Cryptography (LwC) finalists, GIFT-COFB and Photon-Beetle, and present several attacks whose complexities contradict their claimed bounds in their final round specification documents. For GIFT-COFB, we show an attack using $q_e$ encryption queries and no decryption query to break privacy (IND-CPA). The success probability is $O(q_e/2^{n/2})$ for $n$-bit block while the claimed bound contains $O(q^2_e/2^{n})$. This positively...

We propose a general technique to improve the key-guessing step of several attacks on block ciphers. This is achieved by defining and studying some new properties of the associated S-boxes and by representing them as a special type of decision trees that are crucial for finding fine-grained guessing strategies for various attack vectors. We have proposed and implemented the algorithm that efficiently finds such trees, and use it for providing several applications of this approach, which...

The SPEEDY block cipher suite announced at CHES 2021 shows excellent hardware performance. However, SPEEDY was not designed to be efficient in software implementations. SPEEDY's 6-bit sbox and bit permutation operations generally do not work efficiently in software. We implemented SPEEDY block cipher by applying the implementation technique of bit slicing. As an implementation technique of bit slicing, SPEEDY can be operated in software very efficiently and can be applied in...

One of the well-known superiorities of GIFT-64 over PRESENT lies in the correction of the strong linear hull effect. However, apart from the investigation of the 9-round linear hull effect in the design document, we find no linear attack result on GIFT-64. Although we do not doubt the security of GIFT-64 regarding the linear cryptanalysis, the actual resistance of the cipher to the linear attack should be evaluated since it promotes a comprehensive perception of the soundness of GIFT-64....

With the advancement of the quantum computing technologies, a large body of research work is dedicated to revisit the security claims for ciphers being used. An adversary with access to a quantum computer can employ certain new attacks which would not be possible in the current pre-quantum era. In particular, the Grover's search algorithm is a generic attack against symmetric key cryptographic primitives, that can reduce the search complexity to square root. To apply the Grover's search...

When generating quartets for the rectangle attacks on ciphers with linear key-schedule, we find the right quartets which may suggest key candidates have to satisfy some nonlinear relations. However, some quartets generated always violate these relations, so that they will never suggest any key candidates. Inspired by previous rectangle frameworks, we find that guessing certain key cells before generating quartets may reduce the number of invalid quartets. However, guessing a lot of key cells...

GIFT-COFB is a finalist of NIST Lightweight cryptography project that aims at standardizing authenticated encryption schemes for constrained devices. It is a block cipher-based scheme and comes with a provable security result. This paper studies the tightness of the provable security bounds of GIFT-COFB, which roughly tells that, if instantiated by a secure $n$-bit block cipher, we need $2^{n/2}$ encrypted blocks or $2^{n/2}/n$ decryption queries to break the scheme. This paper shows that...

This paper considers the linear cryptanalyses of Authenticated Encryptions with Associated Data (AEADs) GIFT-COFB, SUNDAE-GIFT, and HyENA. All of these proposals take GIFT-128 as underlying primitives. The automatic search with the Boolean satisfiability problem (SAT) method is implemented to search for linear approximations that match the attack settings concerning these primitives. With the newly identified approximations, we launch key-recovery attacks on GIFT-COFB, SUNDAE-GIFT, and HyENA...

COFB is a lightweight Authenticated Encryption with Associated Data (AEAD) mode based on block ciphers. It was proposed in CHES 2017 and is the basis for GIFT-COFB, a finalist in the NIST lightweight standardization project. It comes with provable security results that guarantee its security up to the birthday bound in the nonce-respecting model. However, the designers offer multiple versions of the analysis with different details and the implications of attacks against the scheme are not...

The introduction of the automatic search boosts the cryptanalysis of symmetric-key primitives to some degree. However, the performance of the automatic search is not always satisfactory for the search of long trails or ciphers with large state sizes. Compared with the extensive attention on the enhancement for the search with the mixed integer linear programming (MILP) method, few works care for the acceleration of the automatic search with the Boolean satisfiability problem (SAT) or...

Physical security of NIST lightweight cryptography competition candidates is gaining importance as the standardization process progresses. Side-channel attacks (SCA) are a well-researched topic within the physical security of cryptographic implementations. It was shown that collisions in the intermediate values can be captured by side-channel measurements to reduce the complexity of the key retrieval to trivial numbers. In this paper, we target a specific bit permutation vulnerability in...

Grover's search algorithm gives a quantum attack against block ciphers with query complexity $O(\sqrt{N})$ to search a keyspace of size $N$, when given a sufficient number of plaintext-ciphertext pairs. A recent result by Jaques et al. (EUROCRYPT 2020) presented the cost estimates of quantum key search attacks against AES under different security categories as defined in NIST's PQC standardization process. In this work, we extend their approach to lightweight block ciphers for the cost...

In this article, we analyze and investigate two authenticated encryption algorithms: GIFT-COFB and HyENA. The two modes differ in some low levels details in both the design and security proofs. However, they share a lot of similarities. We take a look at the best-known attacks and security proofs of these designs. We show that the best-known attack is not a matching attack to the security bounds provided by the designers in the security proof. Second, we give a new attack that we...

Mixed Integer Linear Programming (MILP) is a very common method of modelling differential and linear bounds for ciphers, as it automates the process of finding the best differential trail or linear approximation. The Convex Hull (CH) modelling, introduced by Sun et al. (Eprint 2013/Asiacrypt 2014), is a popular method in this regard, which can convert the conditions corresponding to a small (4-bit) SBox to MILP constraints efficiently. In our work, we study this modelling with CH in more...

Grover search algorithm can be used to find the $n$-bit secret key at the speed of $\sqrt{n}$, which is the most effective quantum attack method for block ciphers. In order to apply the Grover search algorithm, the target block cipher should be implemented in quantum circuits. Many recent research works optimized the expensive substitute layer to evaluate the need for quantum resources of AES block ciphers. Research on the implementation of quantum circuits for lightweight block ciphers such...

In this paper, we reevaluate the security of GIFT against differential cryptanalysis under both single-key scenario and related-key scenario. Firstly, we apply Matsui's algorithm to search related-key differential trails of GIFT. We add three constraints to limit the search space and search the optimal related-key differential trails on the limited search space. We obtain related-key differential trails of GIFT-64/128 for up to 15/14 rounds, which are the best results on related-key...

The design and cryptanalysis are the both sides from which we look at symmetric-key primitives. If a symmetric-key primitive is broken by a kind of cryptanalysis, it's definitely insecure. If a designer claims a symmetric-key primitive to be secure, one should demonstrate that the primitive resists against all known attacks. Differential and linear cryptanalysis are two of the most important kinds of cryptanalysis. To conduct a successful differential (linear) cryptanalysis, a differential...

The fixslicing implementation strategy was originally introduced as a new representation for the hardware-oriented GIFT block cipher to achieve very efficient software constant-time implementations. In this article, we show that the fundamental idea underlying the fixslicing technique is not of interest only for GIFT, but can be applied to other ciphers as well. Especially, we study the benefits of fixslicing in the case of AES and show that it allows to reduce by 52% the amount of...

Impossible differentials cryptanalysis and impossible polytopic cryptanalysis are the most effective approaches to estimate the security of block ciphers. However, the previous automatic search methods of their distinguishers, impossible differentials and impossible polytopic transitions, neither consider the impact of key schedule in the single-key setting and the differential property of large S-boxes, nor apply to the block ciphers with variable rotations. Thus, unlike previous methods...

Block ciphers are prevalent in various security protocols used daily such as TLS, OpenPGP, and SSH. Their primary purpose is the protection of user data, both in transit and at rest. One of the de facto methods to evaluate block cipher security is differential cryptanalysis. Differential cryptanalysis observes the propagation of input patterns (input differences) through the cipher to produce output patterns (output differences). This probabilistic propagation is known as a differential; the...

In this article, we propose GIFT-COFB, an Authenticated Encryption with Associated Data (AEAD) scheme, based on the GIFT lightweight block cipher and the COFB lightweight AEAD operating mode. We explain how these two primitives can fit together and the various design adjustments possible for performance and security improvements. We show that our design provides excellent performances in all constrained scenarios, hardware or software, while being based on a provably-secure mode and a well...

GIFT-COFB is one of the round 2 candidate algorithms of NIST lightweight cryptography. In this paper we present a forgery attack on GIFT-COFB. In our attack, the block cipher GIFT is viewed as a block box, and for an arbitrary ciphertext $(C, T)$ with at least twice the block length of GIFT-COFB, if an attacker knows arbitrary two successive blocks of message $M$ corresponding to $C$, he/she can forge infinite new valid ciphertexts $(C', T')$ such that for each $(C', T')$, there exists a...

Bit permutation based block ciphers, like PRESENT and GIFT, are well-known for their extreme lightweightness in hardware implementation. However, designing such ciphers comes with one major challenge - to ensure strong cryptographic properties simply depending on the combination of three components, namely S-box, a bit permutation and a key addition function. Having a wrong combination of components could lead to weaknesses. In this article, we studied the interaction between these...

Cryptographic protections are ubiquitous in information technology, including the emerging Internet of Things (IoT). As a result of technology migration to a resource-challenged landscape and new threats to cryptographic security, governments and industry are exploring new cryptographic algorithms. While new standards will emerge, however, old standards will not disappear for the time being. It is therefore important to explore platforms where multiple cryptographic deployments can be...

The bit-sliding paper of Jean et al. (CHES 2017) showed that the smallest-size circuit for SPN based block ciphers such as AES, SKINNY and PRESENT can be achieved via bit-serial implementations. Their technique decreases the bit size of the datapath and naturally leads to a significant loss in latency (as well as the maximum throughput). Their designs complete a single round of the encryption in 168 (resp. 68) clock cycles for 128 (resp. 64) bit blocks. A follow-up work by Banik et al. (FSE...

The GIFT family of lightweight block ciphers, published at CHES 2017, offers excellent hardware performance figures and has been used, in full or in part, in several candidates of the ongoing NIST lightweight cryptography competition. However, implementation of GIFT in software seems complex and not efficient due to the bit permutation composing its linear layer (a feature shared with PRESENT cipher). In this article, we exhibit a new non-trivial representation of the GIFT family of block...

In this paper, we present all 4-bit S-boxes which are able to support BOGI logic. We exhaustively show that only 2,413 PXE classes of 4-bit S-box are BOGI-applicable among the 142,090,700 PXE classes. We evaluate the whole BOGI-applicable S-boxes in terms of the security and implementation costs. The security evaluation includes security strength of the S-boxes themselves, and how they affect the resistance of GIFT-64 against differential and linear cryptanalysis (DC and LC). The security...

In CHES 2017, Jean et al. presented a paper on ``Bit-Sliding'' in which the authors proposed lightweight constructions for SPN based block ciphers like AES, PRESENT, and SKINNY. The main idea behind these constructions was to reduce the length of the datapath to 1 bit and to reformulate the linear layer for these ciphers so that they require fewer scan flip-flops (which have built-in multiplexer functionality and so larger in area as compared to a simple flip-flop). In this paper, we...

Automatic search methods have been widely used for cryptanalysis of block ciphers, especially for the most classic cryptanalysis methods -- differential and linear cryptanalysis. However, the automatic search methods, no matter based on MILP, SMT/SAT or CP techniques, can be inefficient when the search space is too large. In this paper, we improve Matsui's branch-and-bound search algorithm which is known as the first generic algorithm for finding the best differential and linear trails by...

Achieving security in the Internet of Things (IoT) is challenging. The need for lightweight yet robust cryptographic solutions suitable for the IoT calls for improved design and implementation of constructs such as authenticated encryption with associated data (AEAD) which can ensure confidentiality, integrity, and authenticity of data in one algorithm. The U.S. National Institute of Standards and Technology (NIST) has embarked on a multi-year effort called the lightweight cryptography...

This paper gives a new generalized key-recovery model of related-key rectangle attacks on block ciphers with linear key schedules. The model is quite optimized and applicable to various block ciphers with linear key schedule. As a proof of work, we apply the new model to two very important block ciphers, i.e. SKINNY and GIFT, which are basic modules of many candidates of the Lightweight Cryptography (LWC) standardization project by NIST. For SKINNY, we reduce the complexity of the best...

In Eurocrypt 2018, Cid et al. proposed a novel notion called the boomerang connectivity table, which formalised the switch property in the middle round of boomerang distinguishers in a unified approach. In this paper, we present a generic model of the boomerang connectivity table with automatic search technique for the first time, and search for (related-key) boomerang distinguishers directly by combining with the search of (related-key) differential characteristics. With the technique, we...

When considering practical attacks against cryptographic implementations, Fault Injection Attacks (FIA) pose a powerful tool that can recover the secret key within few encryptions. Over the past few decades they have become a well-studied topic both by academic an industry practitioners. Current state-of-the-art countermeasures against Fault Injection Attacks (FIA) provide good protection against analysis methods that require the differences in the correct and faulty ciphertext to derive...

Tweakable block cipher (TBC), a stronger notion than standard block ciphers, has wide-scale applications in symmetric-key schemes. At a high level, it provides flexibility in design and (possibly) better security bounds. In multi-keyed applications, a TBC with short tweak values can be used to replace multiple keys. However, the existing TBC construction frameworks, including TWEAKEY and XEX, are designed for general purpose tweak sizes. Specifically, they are not optimized for short tweaks,...

Recently, the NIST launched a competition for lightweight cryptography and a large number of ciphers are expected to be studied and analyzed under this competition. Apart from the classical security, the candidates are desired to be analyzed against physical attacks. Differential Fault Analysis (DFA) is an invasive physical attack method for recovering key information from cipher implementations. Up to date, almost all the block ciphers have been shown to be vulnerable against DFA, while...

The automatic search method based on Mix-integer Linear Programming (MILP) is one of the most common tools to search the distinguishers of block ciphers. For differential analysis, the byte-oriented MILP model is usually used to count the number of differential active s-boxes and the bit-oriented MILP model is used to search the optimal differential characteristic. In this paper, we present the influences between the construction and solution of MILP models solved by Gurobi : 1). the number...

Automatic tools have played an important role in designing new cryptographic primitives and evaluating the security of ciphers. Simple Theorem Prover constraint solver (STP) has been used to search for differential/linear trails of ciphers. This paper proposes general STP-based models searching for differential and linear trails with the optimal probability and correlation for S-box based ciphers. In order to get trails with the best probability or correlation for ciphers with arbitrary...

In recent years, Mixed Integer Linear Programming (MILP) has been widely used in cryptanalysis of symmetric-key primitives. For differential and linear cryptanalysis, MILP can be used to solve two kinds of problems: calculation of the minimum number of differentially/linearly active S-boxes, and search for the best differential/linear characteristics. There are already numerous papers published in this area. However, the efficiency is not satisfactory enough for many symmetric-key...

In CHES 2017, Moradi et al. presented a paper on ``Bit-Sliding'' in which the authors proposed lightweight constructions for SPN based block ciphers like AES, Present and SKINNY. The main idea behind these constructions was to reduce the length of the datapath to 1 bit and to reformulate the linear layer for these ciphers so that they require fewer scan flip-flops (which have built-in multiplexer functionality and so larger in area as compared to a simple flip-flop). In this paper we take...

Lightweight block ciphers are today of paramount importance to provide security services in constrained environments. Recent studies have questioned the security properties of PRESENT, which makes it evident the need to study alternative ciphers. In this work we provide hardware architectures for Midori and GIFT, and compare them against implementations for PRESENT and GIMLI under fair conditions. The hardware description for our designs is made publicly available.

This work focuses on side-channel resilient design strategies for symmetric-key cryptographic primitives targeting lightweight applications. In light of NIST's lightweight cryptography project, design choices for block ciphers must consider not only security against traditional cryptanalysis, but also side-channel security, while adhering to low area and power requirements. In this paper, we explore design strategies for substitution-permutation network (SPN)-based block ciphers that make...

The division property method is a technique to determine integral distinguishers on block ciphers. While the complexity of finding these distinguishers is higher, it has recently been shown that MILP and SAT solvers can efficiently find such distinguishers. In this paper, we provide a framework to automatically find those distinguishers which solely requires a description of the cryptographic primitive. We demonstrate that by finding integral distinguishers for 30 primitives with different...

At Asiacrypt 2014, Sun et al. proposed a MILP model to search for differential characteristics of bit-oriented block ciphers. In this paper, we improve this model to search for differential characteristics of GIFT, a new lightweight block cipher proposed at CHES 2017. GIFT has two versions, namely GIFT-64 and GIFT-128. For GIFT-64, we find the best 12-round differential characteristic and a number of iterative 4-round differential characteristics with our MILP-based model. We give a...

Malicious exploitation of faults for extracting secrets is one of the most practical and potent threats to modern cryptographic primitives. Interestingly, not every possible fault for a cryptosystem is maliciously exploitable, and evaluation of the exploitability of a fault is nontrivial. In order to devise precise defense mechanisms against such rogue faults, a comprehensive knowledge is required about the exploitable part of the fault space of a cryptosystem. Unfortunately, the fault space...

Lightweight block ciphers rely on simple operations to allow compact implementation. Thanks to its efficiency, bit permutation has emerged as an optimal choice for state-wise diffusion. It can be implemented by simple wiring or shifts. However, as recently shown by Spectre and Meltdown attacks, efficiency and security often go against each other. In this work, we show how bit permutations introduce a side-channel vulnerability that can be exploited to extract the secret key from the cipher....

By injecting faults, active physical attacks pose serious threats to cryptographic hardware where Concurrent Error Detection (CED) schemes are promising countermeasures. They are usually based on an Error-Detecting Code (EDC) which enables detecting certain injected faults depending on the specification of the underlying code. Here, we propose a methodology to enable correct, practical, and robust implementation of code-based CEDs. We show that straightforward hardware implementations of...

Threshold Implementation (TI) is one of the most widely used countermeasure for side channel attacks. Over the years several TI techniques have been proposed for randomizing cipher execution using different variations of secret-sharing and implementation techniques. For instance, Direct Sharing (4-shares) is the most straightforward implementation of the threshold countermeasure. However, its usage is limited due to its high area requirements. On the other hand, sharing using decomposition...

In this article, we revisit the design strategy of PRESENT, leveraging all the advances provided by the research community in construction and cryptanalysis since its publication, to push the design up to its limits. We obtain an improved version, named GIFT, that provides a much increased efficiency in all domains (smaller and faster), while correcting the well-known weakness of PRESENT with regards to linear hulls. GIFT is a very simple and clean design that outperforms even SIMON or...

This paper presents a lightweight blockcipher based authenticated encryption mode mainly focusing on minimizing the implementation size, i.e., hardware gates or working memory on software. The mode is called COFB, for COmbined FeedBack. COFB uses an $n$-bit blockcipher as the underlying primitive and relies on the use of a nonce for security. In addition to the state required for executing the underlying blockcipher, COFB needs only $n/2$ bits state as a mask. To date, for all existing...

In this article, we revisit the design strategy of PRESENT, leveraging all the advances provided by the research community in construction and cryptanalysis since its publication, to push the design up to its limits. We obtain an improved version, named GIFT, that provides a much increased efficiency in all domains (smaller and faster), while correcting the well-known weakness of PRESENT with regards to linear hulls. GIFT is a very simple and clean design that outperforms even SIMON or...

A coupon is an electronic data that represents the right to access a service provided by a service provider (e.g. gift certificates or movie tickets). Recently, a privacy-protecting multi-coupon system that allows a user to withdraw a predefined number of single coupons from the service provider has been proposed by Chen et al. at Financial Crypto 2005. In this system, every coupon has the same value which is predetermined by the system. The main drawbacks of Chen et al. proposal are that...