The security of lattice-based crytography (LWE, NTRU, and FHE) depends on the hardness of the shortest-vector problem (SVP). Sieving algorithms give the lowest asymptotic runtime to solve SVP, but depend on exponential memory. Memory access costs much more in reality than in the RAM model, so we consider a computational model where processors, memory, and meters of wire are in constant proportions to each other. While this adds substantial costs to route data during lattice sieving, we...

The Hidden Number Problem (HNP) has been extensively used in the side-channel attacks against (EC)DSA and Diffie-Hellman. The lattice approach is a primary method of solving the HNP. In EUROCRYPT 2021, Albrecht and Heninger constructed a new lattice to solve the HNP, which converts the HNP to the SVP. After that, their approach became the state-of-the-art lattice method of solving the HNP. But Albrecht and Heninger's approach has a high failure rate for solving the HNP with one bit of nonce...

The original NTRU cryptosystem from 1998 can be considered the starting point of the great success story of lattice-based cryptography. Modern NTRU versions like NTRU-HPS and NTRU-HRSS are round-3 finalists in NIST's selection process, and also Crystals-Kyber and especially Falcon are heavily influenced by NTRU. Coppersmith and Shamir proposed to attack NTRU via lattice basis reduction, and variations of the Coppersmith-Shamir lattice have been successfully applied to solve official NTRU...

Guo and Johansson (ASIACRYPT 2021), and MATZOV (tech.~report 2022) have independently claimed improved attacks against various NIST lattice candidate by adding a Fast Fourier Transform (FFT) trick on top of the so-called Dual-Sieve attack. Recently, there was more follow up work in this line adding new practical improvements. However, from a theoretical perspective, all of these works are painfully specific to Learning with Errors, while the principle of the Dual-Sieve attack is more...

The Demirci-Sel{\c{c}}uk meet-in-the-middle (DS-MITM) attack is a sophisticated variant of differential attacks. Due to its sophistication, it is hard to efficiently find the best DS-MITM attacks on most ciphers \emph{except} for AES. Moreover, the current automatic tools only capture the most basic version of DS-MITM attacks, and the critical techniques developed for enhancing the attacks (e.g., differential enumeration and key-dependent-sieve) still rely on manual work. In...

The problem of decoding random codes is a fundamental problem for code-based cryptography, including recent code-based candidates in the NIST post-quantum standardization process. In this paper, we present a novel sieving-style information-set decoding (ISD) algorithm, addressing the task of solving the syndrome decoding problem. Our approach involves maintaining a list of weight-$2p$ solution vectors to a partial syndrome decoding problem and then creating new vectors by identifying pairs...

The unique Shortest Vector Problem (uSVP) is one of the core hard problems in lattice-based cryptography. In NIST PQC standardization (Kyber, Dilithium), leaky-LWE-Estimator is used to estimate the hardness of LWE-based cryptosystems by reducing LWE to uSVP and considers the primal attack using Progressive BKZ (ProBKZ). ProBKZ trivially increases blocksize β and lifts the shortest vector in the final BKZ block to find the unique shortest vector in the full lattice. In this paper, we...

The General Sieve Kernel (G6K) implemented a variety of lattice reduction algorithms based on sieving algorithms. One of the representative of these lattice reduction algorithms is Pump and jump-BKZ (pnj-BKZ) algorithm which is currently considered as the fastest lattice reduction algorithm. The pnj-BKZ is a BKZ-type lattice reduction algorithm which includes the jump strategy, and uses Pump as the SVP Oracle. Here, Pump which was also proposed in G6K, is an SVP sloving algorithm that...

The asymptotically fastest known method for solving SVP is via lattice sieving, an algorithm whose computational bottleneck is solving the Nearest Neighbor Search problem. The best known algorithm for solving this problem is Hypercone Locality Sensitive Filtering (LSF). The classical time complexity of a sieve using Hypercone LSF is \(2^{0.2925d+o(d)}\). The quantum time complexity is \(2^{0.2653d+o(d)}\), which is acquired by using Grover's algorithm to speed up part of the enumeration. We...

The Learning with Errors problem (LWE) has become a central topic in recent cryptographic research. In this paper, we present a new solving algorithm combining important ideas from previous work on improving the Blum-Kalai-Wasserman (BKW) algorithm and ideas from sieving in lattices. The new algorithm is analyzed and demonstrates an improved asymptotic performance. For the Regev parameters $q=n^2$ and noise level $\sigma = n^{1.5}/(\sqrt{2\pi}\log_{2}^{2}n)$, the asymptotic complexity is...

Most algorithms for hard lattice problems are based on the principle of rank reduction: to solve a problem in a $d$-dimensional lattice, one first solves one or more problem instances in a sublattice of rank $d - 1$, and then uses this information to find a solution to the original problem. Existing lattice sieving methods, however, tackle lattice problems such as the shortest vector problem (SVP) directly, and work with the full-rank lattice from the start. Lattice sieving further seems to...

We present an algorithm for the approximate $k$-List problem for the Euclidean distance that improves upon the Bai-Laarhoven-Stehle (BLS) algorithm from ANTS'16. The improvement stems from the observation that almost all the solutions to the approximate $k$-List problem form a particular configuration in $n$-dimensional space. Due to special properties of configurations, it is much easier to verify whether a $k$-tuple forms a configuration rather than checking whether it gives a solution to...

Akleylek et al have proposed Ring-TESLA, a practical and efficient digital signature scheme based on the Ring Learning With Errors problem. However we have identified there are some problems with the parameters proposed for Ring-TESLA, as we believe they do not ensure the correct operation of the scheme and do not provide the targeted levels of security under either the provable Ring-TESLA reduction, or an assessment of practical modern attacks such as lattice sieving. We recommend new...

Kalyna is an SPN-based block cipher that was selected during Ukrainian National Public Cryptographic Competition (2007-2010) and its slight modification was approved as the new encryption standard of Ukraine. In this paper, we focus on the key-recovery attacks on reduced-round Kalyna-128/256 and Kalyna-256/512 with meet-in-the-middle method. The differential enumeration technique and key-dependent sieve technique which are popular to analyze AES are used to attack them. Using the ...

In a recent work, Kim and Barbulescu showed how to combine previous polynomial selection methods with the extended tower number field sieve algorithm to obtain improved complexity for the discrete logarithm problem on finite fields $\mathbb{F}_{p^n}$ for the medium prime case and where $n$ is composite and not a prime-power. A follow up work by Sarkar and Singh presented a general polynomial selection method and showed how to lower the complexity in the medium prime case even when $n$ is...

In a recent work, Kim and Barbulescu had extended the tower number field sieve algorithm to obtain improved asymptotic complexities in the medium prime case for the discrete logarithm problem on $\mathbb{F}_{p^n}$ where $n$ is not a prime power. Their method does not work when $n$ is a composite prime power. For this case, we obtain new asymptotic complexities, e.g., $L_{p^n}(1/3,(64/9)^{1/3})$ (resp. $L_{p^n}(1/3,1.88)$ for the multiple number field variation) when $n$ is composite and a...

The meet-in-the-middle (MITM) attack has prove to be efficient in analyzing the AES block cipher. Its efficiency has been increasing with the introduction of various techniques such as differential enumeration, key-dependent sieve, super-box etc. The recent MITM attack given by Li and Jin has successfully mounted to 10-round AES-256. Crypton is an AES-like block cipher. In this paper, we apply the MITM method to the cryptanalysis of Crypton-256. Following Li and Jin's idea, we give the...

The Number Field Sieve (NFS) algorithm is the best known method to compute discrete logarithms (DL) in finite fields $\mathbb{F}_{p^n}$, with $p$ medium to large and $n \geq 1$ small. This algorithm comprises four steps: polynomial selection, relation collection, linear algebra and finally, individual logarithm computation. The first step outputs two polynomials defining two number fields, and a map from the polynomial ring over the integers modulo each of these polynomials to...

The function field sieve, a subexponential algorithm of complexity L(1/3) that computes discrete logarithms in finite fields, has recently been improved to an algorithm of complexity L(1/4) and subsequently to a quasi-polynomial time algorithm. We investigate whether the new ideas also apply to index calculus algorithms for computing discrete logarithms in Jacobians of algebraic curves. While we do not give a final answer to the question, we discuss a number of ideas, experiments, and...

By applying a quantum search algorithm to various heuristic and provable sieve algorithms from the literature, we obtain improved asymptotic quantum results for solving the shortest vector problem on lattices. With quantum computers we can provably find a shortest vector in time $2^{1.799n + o(n)}$, improving upon the classical time complexities of $2^{2.465n + o(n)}$ of Pujol and Stehlé and the $2^{2n + o(n)}$ of Micciancio and Voulgaris, while heuristically we expect to find a shortest...

In this short paper, we propose a variant of the Number Field Sieve to compute discrete logarithms in medium characteristic finite fields. We propose an algorithm that combines two recent ideas, namely the Multiple variant of the Number Field Sieve taking advantage of a large number of number fields in the sieving phase and the Conjugation Method giving a new polynomial selection for the classical Number Field Sieve. The asymptotic complexity of our improved algorithm is L_Q (1/3, (8 (9+4...

In this paper, we study the discrete logarithm problem in medium and high characteristic finite fields. We propose a variant of the Number Field Sieve (NFS) based on numerous number fields. Our improved algorithm computes discrete logarithms in $\mathbb{F}_{p^n}$ for the whole range of applicability of NFS and lowers the asymptotic complexity from $L_{p^n}(1/3, (128/9)^{1/3})$ to $L_{p^n}(1/3, (2^{13} /3^6)^{1/3})$ in the medium characteristic case, and from $L_{p^n} (1/3, (64/9)^{1/3})$ to...

In this paper, we describe new techniques in meet-in-the-middle attacks. Our basic technique is called a \emph{linear key sieve} since it exploits as filtering conditions linear dependencies between key bits that are guessed from both sides of the attack. This should be contrasted with related previous attacks, which only exploited a \emph{linear state sieve} (i.e., linear dependencies between state bits that are computed from both sides of the attack). We apply these techniques to the...

In this paper, we study the discrete logarithm problem in finite fields related to pairing-based curves. We start with a precise analysis of the state-of-the-art algorithms for computing discrete logarithms that are suitable for finite fields related to pairing-friendly constructions. To improve upon these algorithms, we extend the Special Number Field Sieve to compute discrete logarithms in $\F_{p^{n}}$, where $p$ has an adequate sparse representation. Our improved algorithm works for the...

This paper studies key-recovery attacks on AES-192 and PRINCE under single-key model by methodology of meet-in-the-middle attack. A new technique named key-dependent sieve is proposed to further reduce the memory complexity of Demirci et al.'s attack at EUROCRYPT 2013, which helps us to achieve 9-round attack on AES-192 by using a 5-round distinguisher; the data, time and memory complexities are 2^{121} chosen plaintexts, 2^{185} encryptions and 2^{185} 128- bit memories, respectively. The...

This paper presents a new generic technique, named sieve-in-the-middle, which improves meet-in-the-middle attacks in the sense that it provides an attack on a higher number of rounds. Instead of selecting the key candidates by searching for a collision in an intermediate state which can be computed forwards and backwards, we here look for the existence of valid transitions through some middle sbox. Combining this technique with short bicliques allows to freely add one or two more rounds with...

Many index calculus algorithms generate multiplicative relations between smoothness basis elements by using a process called {\it Sieving}. This process allows to filter potential candidate relations very quickly, without spending too much time to consider bad candidates. However, from an asymptotic point of view, there is not much difference between sieving and straightforward testing of candidates. The reason is that even when sieving, some small amount time is spend for each bad...

There are many useful cryptographic schemes, such as ID-based encryption, short signature, keyword searchable encryption, attribute-based encryption, functional encryption, that use a bilinear pairing. It is important to estimate the security of such pairing-based cryptosystems in cryptography. The most essential number-theoretic problem in pairing-based cryptosystems is the discrete logarithm problem (DLP) because pairing-based cryptosystems are no longer secure once the underlining DLP is...

The security of pairing-based cryptosystems depends on the difficulty of the discrete logarithm problem (DLP) over certain types of finite fields. One of the most efficient algorithms for computing a pairing is the $\eta_T$ pairing over supersingular curves on finite fields whose characteristic is $3$. Indeed many high-speed implementations of this pairing have been reported, and it is an attractive candidate for practical deployment of pairing-based cryptosystems. The embedding degree of...

We describe improved versions of index-calculus algorithms for solving discrete logarithm problems in Jacobians of high-genus hyperelliptic curves defined over even characteristic fields. Our first improvement is to incorporate several ideas for the low-genus case by Gaudry and Theriault, including the large prime variant and using a smaller factor base, into the large-genus algorithm of Enge and Gaudry. We extend the analysis in [24] to our new algorithm, allowing us to predict accurately...

In this paper, we present an improvement of the Nguyen-Vidick heuristic sieve algorithm for shortest vector problem in general lattices, which time complexity is 2^0.3836n polynomial computations, and space complexity is 2^0.2557n. In the new algorithm, we introduce a new sieve technique with two-level instead of the previous one-level sieve, and complete the complexity estimation by calculating the irregular spherical cap covering.

This paper presents an improved impossible differential attack on the new block cipher CLEFIA which is proposed by Sony Corporation at FSE 2007. Combining some observations with new tricks, we can filter out the wrong keys more efficiently, and improve the impossible differential attack on 11-round CLEFIA-192/256, which also firstly works for CLEFIA-128. The complexity is about $2^{103.1}$ encryptions and $2^{103.1}$ chosen plaintexts. By putting more constraint conditions on plaintext...