Security analysis of NIST-LWC contest finalists

Dissertação de mestrado integrado em Informatics EngineeringTraditional cryptographic standards are designed with a desktop and server environment in mind, so, with the relatively recent proliferation of small, resource constrained devices in the Internet of Things, sensor networks, embedded systems, and more, there has been a call for lightweight cryptographic standards with security, performance and resource requirements tailored for the highly-constrained environments these devices find themselves in. In 2015 the National Institute of Standards and Technology began a Standardization Process in order to select one or more Lightweight Cryptographic algorithms. Out of the original 57 submissions ten finalists remain, with ASCON and Romulus being among the most scrutinized out of them. In this dissertation I will introduce some concepts required for easy understanding of the body of work, do an up-to-date revision on the current situation on the standardization process from a security and performance standpoint, a description of ASCON and Romulus, and new best known analysis, and a comparison of the two, with their advantages, drawbacks, and unique traits.Os padrões criptográficos tradicionais foram elaborados com um ambiente de computador e servidor em mente. Com a proliferação de dispositivos de pequenas dimensões tanto na Internet of Things, redes de sensores e sistemas embutidos, apareceu uma necessidade para se definir padrões para algoritmos de criptografia leve, com prioridades de segurança, performance e gasto de recursos equilibrados para os ambientes altamente limitados em que estes dispositivos operam. Em 2015 o National Institute of Standards and Technology lançou um processo de estandardização com o objectivo de escolher um ou mais algoritmos de criptografia leve. Das cinquenta e sete candidaturas originais sobram apenas dez finalistas, sendo ASCON e Romulus dois desses finalistas mais examinados. Nesta dissertação irei introduzir alguns conceitos necessários para uma fácil compreensão do corpo deste trabalho, assim como uma revisão atualizada da situação atual do processo de estandardização de um ponto de vista tanto de segurança como de performance, uma descrição do ASCON e do Romulus assim como as suas melhores análises recentes e uma comparação entre os dois, frisando as suas vantagens, desvantagens e aspectos únicos

Integral Distinguishers for Reduced-round Stribog

In January 2013, the Stribog hash function officially replaced GOST R 34.11-94 as the new Russian cryptographic hash standard GOST R 34.11-2012. Stribog is an AES-based primitive and is considered as an asymmetric reply to the new SHA-3 selected by NIST. In this paper we investigate the structural integral properties of reduced version of the Stribog compression function and its internal permutation. Specifically, we present a forward and backward higher order integrals that can be used to distinguish 4 and 3.5 rounds, respectively. Moreover, using the start from the middle approach, we combine the two proposed integrals to get 6.5-round and 7.5-round distinguishers for the internal permutation and 6-round and 7-round distinguishers for the compression function

Zero-Sum Distinguishers for Iterated Permutations and Application to Keccak-f and Hamsi-256

International audienceThe zero-sum distinguishers introduced by Aumasson and Meier are investigated. First, the minimal size of a zero-sum is established. Then, we analyze the impacts of the linear and the nonlinear layers in an iterated permutation on the construction of zero-sum partitions. Finally, these techniques are applied to the Keccak-f permutation and to Hamsi-256. We exhibit several zero-sum partitions for 20 rounds (out of 24) of Keccak-f and some zero-sum partitions of size 2^{19} and 2^{10} for the finalization permutation in Hamsi-256

Cryptanalysis of Some AES-based Cryptographic Primitives

Current information security systems rely heavily on symmetric key cryptographic primitives as one of their basic building blocks. In order to boost the efficiency of the security systems, designers of the underlying primitives often tend to avoid the use of provably secure designs. In fact, they adopt ad hoc designs with claimed security assumptions in the hope that they resist known cryptanalytic attacks. Accordingly, the security evaluation of such primitives continually remains an open field. In this thesis, we analyze the security of two cryptographic hash functions and one block cipher. We primarily focus on the recent AES-based designs used in the new Russian Federation cryptographic hashing and encryption suite GOST because the majority of our work was carried out during the open research competition run by the Russian standardization body TC26 for the analysis of their new cryptographic hash function Streebog. Although, there exist security proofs for the resistance of AES- based primitives against standard differential and linear attacks, other cryptanalytic techniques such as integral, rebound, and meet-in-the-middle attacks have proven to be effective. The results presented in this thesis can be summarized as follows: Initially, we analyze various security aspects of the Russian cryptographic hash function GOST R 34.11-2012, also known as Streebog or Stribog. In particular, our work investigates five security aspects of Streebog. Firstly, we present a collision analysis of the compression function and its in- ternal cipher in the form of a series of modified rebound attacks. Secondly, we propose an integral distinguisher for the 7- and 8-round compression function. Thirdly, we investigate the one wayness of Streebog with respect to two approaches of the meet-in-the-middle attack, where we present a preimage analysis of the compression function and combine the results with a multicollision attack to generate a preimage of the hash function output. Fourthly, we investigate Streebog in the context of malicious hashing and by utilizing a carefully tailored differential path, we present a backdoored version of the hash function where collisions can be generated with practical complexity. Lastly, we propose a fault analysis attack which retrieves the inputs of the compression function and utilize it to recover the secret key when Streebog is used in the keyed simple prefix and secret-IV MACs, HMAC, or NMAC. All the presented results are on reduced round variants of the function except for our analysis of the malicious version of Streebog and our fault analysis attack where both attacks cover the full round hash function. Next, we examine the preimage resistance of the AES-based Maelstrom-0 hash function which is designed to be a lightweight alternative to the ISO standardized hash function Whirlpool. One of the distinguishing features of the Maelstrom-0 design is the proposal of a new chaining construction called 3CM which is based on the 3C/3C+ family. In our analysis, we employ a 4-stage approach that uses a modified technique to defeat the 3CM chaining construction and generates preimages of the 6-round reduced Maelstrom-0 hash function. Finally, we provide a key recovery attack on the new Russian encryption standard GOST R 34.12- 2015, also known as Kuznyechik. Although Kuznyechik adopts an AES-based design, it exhibits a faster diffusion rate as it employs an optimal diffusion transformation. In our analysis, we propose a meet-in-the-middle attack using the idea of efficient differential enumeration where we construct a three round distinguisher and consequently are able to recover 16-bytes of the master key of the reduced 5-round cipher. We also present partial sequence matching, by which we generate, store, and match parts of the compared parameters while maintaining negligible probability of matching error, thus the overall online time complexity of the attack is reduced

Quantum Speed-Up for Multidimensional (Zero Correlation) Linear Distinguishers

This paper shows how to achieve a quantum speed-up for multidimensional (zero correlation) linear distinguishers. A previous work by Kaplan et al. has already shown a quantum quadratic speed-up for one-dimensional linear distinguishers. However, classical linear cryptanalysis often exploits multidimensional approximations to achieve more efficient attacks, and in fact it is highly non-trivial whether Kaplan et al.\u27s technique can be extended into the multidimensional case. To remedy this, we investigate a new quantum technique to speed-up multidimensional linear distinguishers. Firstly, we observe that there is a close relationship between the subroutine of Simon\u27s algorithm and linear correlations via Fourier transform. Specifically, a slightly modified version of Simon\u27s subroutine, which we call Correlation Extraction Algorithm (CEA), can be used to speed-up multidimensional linear distinguishers. CEA also leads to a speed-up for multidimensional zero correlation distinguishers, as well as some integral distinguishers through the correspondence of zero correlation and integral properties shown by Bogdanov et al.~and Sun et al. Furthermore, we observe possibility of a more than quadratic speed-ups for some special types of integral distinguishers when multiple integral properties exist. Especially, we show a single-query distinguisher on a 4-bit cell SPN cipher with the same integral property as 2.5-round AES. Our attacks are the first to observe such a speed-up for classical cryptanalytic techniques without relying on hidden periods or shifts. By replacing the Hadamard transform in CEA with the general quantum Fourier transform, our technique also speeds-up generalized linear distinguishers on an arbitrary finite abelian group

MOIM: a novel design of cryptographic hash function

A hash function usually has two main components: a compression function or permutation function and mode of operation. In this paper, we propose a new concrete novel design of a permutation based hash functions called MOIM. MOIM is based on concatenating two parallel fast wide pipe constructions as a mode of operation designed by Nandi and Paul, and presented at Indocrypt 2010 where the size of the internal state is significantly larger than the size of the output. And the permutations functions used in MOIM are inspired from the SHA-3 finalist Grøstl hash function which is originally inspired from Rijndael design (AES). As a consequence there is a very strong confusion and diffusion in MOIM. Also, we show that MOIM resists all the generic attacks and Joux attack in two defense security levels

Weak Keys in Reduced AEGIS and Tiaoxin

AEGIS-128 and Tiaoxin-346 (Tiaoxin for short) are two AES-based primitives submitted to the CAESAR competition. Among them, AEGIS-128 has been selected in the final portfolio for high-performance applications, while Tiaoxin is a third-round candidate. Although both primitives adopt a stream cipher based design, they are quite different from the well-known bit-oriented stream ciphers like Trivium and the Grain family. Their common feature consists in the round update function, where the state is divided into several 128-bit words and each word has the option to pass through an AES round or not. During the 6-year CAESAR competition, it is surprising that for both primitives there is no third-party cryptanalysis of the initialization phase. Due to the similarities in both primitives, we are motivated to investigate whether there is a common way to evaluate the security of their initialization phases. Our technical contribution is to write the expressions of the internal states in terms of the nonce and the key by treating a 128-bit word as a unit and then carefully study how to simplify these expressions by adding proper conditions. As a result, we find that there are several groups of weak keys with 296 keys each in 5-round AEGIS-128 and 8-round Tiaoxin, which allows us to construct integral distinguishers with time complexity 232 and data complexity 232. Based on the distinguisher, the time complexity to recover the weak key is 272 for 5-round AEGIS-128. However, the weak key recovery attack on 8-round Tiaoxin will require the usage of a weak constant occurring with probability 2−32. All the attacks reach half of the total number of initialization rounds. We expect that this work can advance the understanding of the designs similar to AEGIS and Tiaoxin

Automatic Search of Bit-Based Division Property for ARX Ciphers and Word-Based Division Property

Division property is a generalized integral property proposed by Todo at Eurocrypt 2015. Previous tools for automatic searching are mainly based on the Mixed Integer Linear Programming (MILP) method and trace the division property propagation at the bit level. In this paper, we propose automatic tools to detect ARX ciphers\u27 division property at the bit level and some specific ciphers\u27 division property at the word level. For ARX ciphers, we construct the automatic searching tool relying on Boolean Satisfiability Problem (SAT) instead of MILP, since SAT method is more suitable in the search of ARX ciphers\u27 differential/linear characteristics. The propagation of division property is translated into a system of logical equations in Conjunctive Normal Form (CNF). Some logical equations can be dynamically adjusted according to different initial division properties and stopping rule, while the others corresponding to r-round propagations remain the same. Moreover, our approach can efficiently identify some optimized distinguishers with lower data complexity. As a result, we obtain a 17-round distinguisher for SHACAL-2, which gains four more rounds than previous work, and an 8-round distinguisher for LEA, which covers one more round than the former one. For word-based division property, we develop the automatic search based on Satisfiability Modulo Theories (SMT), which is a generalization of SAT. We model division property propagations of basic operations and S-boxes by logical formulas, and turn the searching problem into an SMT problem. With some available solvers, we achieve some new distinguishers. For CLEFIA, 10-round distinguishers are obtained, which cover one more round than the previous work. For the internal block cipher of Whirlpool, the data complexities of 4/5-round distinguishers are improved. For Rijndael-192 and Rijndael-256, 6-round distinguishers are presented, which attain two more rounds than the published ones. Besides, the integral attacks for CLEFIA are improved by one round with the newly obtained distinguishers