Fault Analysis of Kuznyechik

Kuznyechik is an SPN block cipher that has been chosen recently to be standardized by the Russian federation as a new GOST cipher. In this paper, we present two fault analysis attacks on two different settings of the cipher. The first attack is a differential fault attack which employs the random byte fault model, where the attacker is assumed to be able to fault a random byte in rounds seven and eight. Using this fault model enables the attacker to recover the master key using an average of four faults. The second attack considers the cipher with a secret sbox. By utilizing an ineffective fault analysis in the byte stuck-at-zero fault model, we present a four stage attack to recover both the master key and the secret sbox parameters. Our second attack is motivated by the fact that, similar to GOST 28147-89, Kuznyechik is expected to include the option of using secret sbox based on the user supplied key to increase its security margin. Both the presented attacks have practical complexities and aim to demonstrate the importance of protecting the hardware and software implementations of the new standard even if its sbox is kept secret

Design and Cryptanalysis of Symmetric-Key Algorithms in Black and White-box Models

Cryptography studies secure communications. In symmetric-key cryptography, the communicating parties have a shared secret key which allows both to encrypt and decrypt messages. The encryption schemes used are very efficient but have no rigorous security proof. In order to design a symmetric-key primitive, one has to ensure that the primitive is secure at least against known attacks. During 4 years of my doctoral studies at the University of Luxembourg under the supervision of Prof. Alex Biryukov, I studied symmetric-key cryptography and contributed to several of its topics. Part I is about the structural and decomposition cryptanalysis. This type of cryptanalysis aims to exploit properties of the algorithmic structure of a cryptographic function. The first goal is to distinguish a function with a particular structure from random, structure-less functions. The second goal is to recover components of the structure in order to obtain a decomposition of the function. Decomposition attacks are also used to uncover secret structures of S-Boxes, cryptographic functions over small domains. In this part, I describe structural and decomposition cryptanalysis of the Feistel Network structure, decompositions of the S-Box used in the recent Russian cryptographic standard, and a decomposition of the only known APN permutation in even dimension. Part II is about the invariant-based cryptanalysis. This method became recently an active research topic. It happened mainly due to recent extreme cryptographic designs, which turned out to be vulnerable to this cryptanalysis method. In this part, I describe an invariant-based analysis of NORX, an authenticated cipher. Further, I show a theoretical study of linear layers that preserve low-degree invariants of a particular form used in the recent attacks on block ciphers. Part III is about the white-box cryptography. In the white-box model, an adversary has full access to the cryptographic implementation, which in particular may contain a secret key. The possibility of creating implementations of symmetric-key primitives secure in this model is a long-standing open question. Such implementations have many applications in industry; in particular, in mobile payment systems. In this part, I study the possibility of applying masking, a side-channel countermeasure, to protect white-box implementations. I describe several attacks on direct application of masking and provide a provably-secure countermeasure against a strong class of the attacks. Part IV is about the design of symmetric-key primitives. I contributed to design of the block cipher family SPARX and to the design of a suite of cryptographic algorithms, which includes the cryptographic permutation family SPARKLE, the cryptographic hash function family ESCH, and the authenticated encryption family SCHWAEMM. In this part, I describe the security analysis that I made for these designs

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

Practical-Time Related-Key Attack on GOST with Secret S-boxes

The block cipher GOST 28147-89 was the Russian Federation encryption standard for over 20 years, and is still one of its two standard block ciphers. GOST is a 32-round Feistel construction, whose security benefits from the fact that the S-boxes used in the design are kept secret. In the last 10 years, several attacks on the full 32-round GOST were presented. However, they all assume that the S-boxes are known. When the S-boxes are secret, all published attacks either target a small number of rounds, or apply for small sets of weak keys. In this paper we present the first practical-time attack on GOST with secret S-boxes. The attack works in the related-key model and is faster than all previous attacks in this model which assume that the S-boxes are known. The complexity of the attack is less than $2^{27}$ encryptions. It was fully verified, and runs in a few seconds on a PC. The attack is based on a novel type of related-key differentials of GOST, inspired by local collisions. Our new technique may be applicable to certain GOST-based hash functions as well. To demonstrate this, we show how to find a collision on a Davies-Meyer construction based on GOST with an arbitrary initial value, in less than $2^{10}$ hash function evaluations

A Salad of Block Ciphers

This book is a survey on the state of the art in block cipher design and analysis. It is work in progress, and it has been for the good part of the last three years -- sadly, for various reasons no significant change has been made during the last twelve months. However, it is also in a self-contained, useable, and relatively polished state, and for this reason I have decided to release this \textit{snapshot} onto the public as a service to the cryptographic community, both in order to obtain feedback, and also as a means to give something back to the community from which I have learned much. At some point I will produce a final version -- whatever being a ``final version\u27\u27 means in the constantly evolving field of block cipher design -- and I will publish it. In the meantime I hope the material contained here will be useful to other people

Proceedings of FORM 2022. Construction The Formation of Living Environment

This study examines the integration of building information modelling (BIM) technologies in operation & maintenance stage in the system of managing real estate that helps to reduce transaction costs. The approach and method are based on Digital Twin technology and Model Based System Engineering (MBSE) approach. The results of the development of a service for digital facility management and digital expertise are presented. The connection between physical and digital objects is conceptualized

Cryptanalysis of Some Block Cipher Constructions

When the public-key cryptography was introduced in the 1970s, symmetric-key cryptography was believed to soon become outdated. Nevertheless, we still heavily rely on symmetric-key primitives as they give high-speed performance. They are used to secure mobile communication, e-commerce transactions, communication through virtual private networks and sending electronic tax returns, among many other everyday activities. However, the security of symmetric-key primitives does not depend on a well-known hard mathematical problem such as the factoring problem, which is the basis of the RSA public-key cryptosystem. Instead, the security of symmetric-key primitives is evaluated against known cryptanalytic techniques. Accordingly, the topic of furthering the state-of-the-art of cryptanalysis of symmetric-key primitives is an ever-evolving topic. Therefore, this thesis is dedicated to the cryptanalysis of symmetric-key cryptographic primitives. Our focus is on block ciphers as well as hash functions that are built using block ciphers. Our contributions can be summarized as follows: First, we tackle the limitation of the current Mixed Integer Linear Programming (MILP) approaches to represent the differential propagation through large S-boxes. Indeed, we present a novel approach that can efficiently model the Difference Distribution Table (DDT) of large S-boxes, i.e., 8-bit S-boxes. As a proof of the validity and efficiency of our approach, we apply it on two out of the seven AES-round based constructions that were recently proposed in FSE 2016. Using our approach, we improve the lower bound on the number of active S-boxes of one construction and the upper bound on the best differential characteristic of the other. Then, we propose meet-in-the-middle attacks using the idea of efficient differential enumeration against two Japanese block ciphers, i.e., Hierocrypt-L1 and Hierocrypt-3. Both block ciphers were submitted to the New European Schemes for Signatures, Integrity, and Encryption (NESSIE) project, selected as one of the Japanese e-Government recommended ciphers in 2003 and reselected in the candidate recommended ciphers list in 2013. We construct five S-box layer distinguishers that we use to recover the master keys of reduced 8 S-box layer versions of both block ciphers. In addition, we present another meet-in-the-middle attack on Hierocrypt-3 with slightly higher time and memory complexities but with much less data complexity. Afterwards, we shift focus to another equally important cryptanalytic attack, i.e., impossible differential attack. SPARX-64/128 is selected among the SPARX family that was recently proposed to provide ARX based block cipher whose security against differential and linear cryptanalysis can be proven. We assess the security of SPARX-64/128 against impossible differential attack and show that it can reach the same number of rounds the division-based integral attack, proposed by the designers, can reach. Then, we pick Kiasu-BC as an example of a tweakable block cipher and prove that, on contrary to its designers’ claim, the freedom in choosing the publicly known tweak decreases its security margin. Lastly, we study the impossible differential properties of the underlying block cipher of the Russian hash standard Streebog and point out the potential risk in using it as a MAC scheme in the secret-IV mode

Side-Channel Analysis and Cryptography Engineering : Getting OpenSSL Closer to Constant-Time

As side-channel attacks reached general purpose PCs and started to be more practical for attackers to exploit, OpenSSL adopted in 2005 a flagging mechanism to protect against SCA. The opt-in mechanism allows to flag secret values, such as keys, with the BN_FLG_CONSTTIME flag. Whenever a flag is checked and detected, the library changes its execution flow to SCA-secure functions that are slower but safer, protecting these secret values from being leaked. This mechanism favors performance over security, it is error-prone, and is obscure for most library developers, increasing the potential for side-channel vulnerabilities. This dissertation presents an extensive side-channel analysis of OpenSSL and criticizes its fragile flagging mechanism. This analysis reveals several flaws affecting the library resulting in multiple side-channel attacks, improved cache-timing attack techniques, and a new side channel vector. The first part of this dissertation introduces the main topic and the necessary related work, including the microarchitecture, the cache hierarchy, and attack techniques; then it presents a brief troubled history of side-channel attacks and defenses in OpenSSL, setting the stage for the related publications. This dissertation includes seven original publications contributing to the area of side-channel analysis, microarchitecture timing attacks, and applied cryptography. From an SCA perspective, the results identify several vulnerabilities and flaws enabling protocol-level attacks on RSA, DSA, and ECDSA, in addition to full SCA of the SM2 cryptosystem. With respect to microarchitecture timing attacks, the dissertation presents a new side-channel vector due to port contention in the CPU execution units. And finally, on the applied cryptography front, OpenSSL now enjoys a revamped code base securing several cryptosystems against SCA, favoring a secure-by-default protection against side-channel attacks, instead of the insecure opt-in flagging mechanism provided by the fragile BN_FLG_CONSTTIME flag

A Formula for Disaster : A Unified Approach to Elliptic Curve Special-Point-Based Attacks

The Refined Power Analysis, Zero-Value Point, and Exceptional Procedure attacks introduced side-channel techniques against specific cases of elliptic curve cryptography. The three attacks recover bits of a static ECDH key adaptively, collecting information on whether a certain multiple of the input point was computed. We unify and generalize these attacks in a common framework, and solve the corresponding problem for a broader class of inputs. We also introduce a version of the attack against windowed scalar multiplication methods, recovering the full scalar instead of just a part of it. Finally, we systematically analyze elliptic curve point addition formulas from the Explicit-Formulas Database, classify all non-trivial exceptional points, and find them in new formulas. These results indicate the usefulness of our tooling, which we released publicly, for unrolling formulas and finding special points, and potentially for independent future work.acceptedVersionPeer reviewe