International Workshop on Dynamical Systems and Applications

Konuşma Özetleri



Speaker: Elena Andreeva

Title: Security Aspects of Authenticated Encryption

Abstract: Traditionally, the two main cryptographic goals of confidentiality and integrity are realized separately by encryption and authentication schemes, respectively. The current trend in cryptography is to use a single algorithm for both; namely, an authenticated encryption (AE) scheme. The demand for secure and efficient AE schemes is reflected in the ongoing CAESAR cryptographic competition for the recommendation of a portfolio of AE algorithms.

In this talk we will give an overview of the existing AE design methods such as generic composition and dedicated approaches. We will cover the target AE security definitions and further we will discuss a number of security vulnerabilities and their possible solutions. Finally, we will focus on the CAESAR competition by presenting some of the candidates, their features and comparisons.


Speaker: Neşe Koçak

Title: Bent and Semi-bent Functions

Abstract: B​ent and semi-bent functions ​have an important role in cryptography. They are widely studied as parts of building blocks in symmetric key cryptosystems because they provide resistance to fast correlation attacks and linear cryptanalysis due to their high nonlinearity. Therefore, c​onstruction and classification of these functions are very significant. In this talk, the concepts related to bent and semi-bent functions are mentioned and results on characterization and enumeration of these functions are presented.



Speaker: Hüseyin Demirci

Title: Human cipher and genomic privacy

Abstract: With the completion of the Human Genome Project, our understanding of health and disease began to change significantly. We are approaching a near future that all of us will be ‘sequenced’. In this talk we will introduce this new era and talk about a cipher modeling for the human organism. We will introduce some analogies between cipher analysis methods and genomic studies. Finally, we will briefly point out some privacy concerns of this upcoming genomic era.


Speaker: Cihangir Tezcan

Title: New Evaluation Criteria for S-boxes

Abstract: Confusion layer of symmetric cryptography algorithms mostly consists of substitution boxes (S-boxes) and in order to provide better security against known attacks, S-boxes are selected depending on their cryptographic properties. Although there are many cryptographic properties of S-boxes, algorithm designers mostly focus on only the differential and non-linear uniformity. In this talk, we will first summarize the known cryptographic properties of S-boxes. Then we will describe our two recently introduced S-box properties: Differential factors and undisturbed bits. Differential factors prevent the attacker to distinguish some of the guessed keys corresponding to an active S-box during a differential attack on a block cipher and they can be used to reduce the data and time complexities of these attacks. Undisturbed bits can be used to obtain better truncated, impossible, and improbable differentials. As an example, we will provide 5-round distinguishers for ASCON using undisturbed bits.




Speaker: Beyza Bozdemir

Title: Improvement on Bit Diffusion Analysis of π-Cipher

Abstract: π-Cipher, designed by Gligoroski et al., is a second round candidate of the CAESAR competition. The designers analyzed the bit diffusion of the cipher by examining the ∗ operation and 1 round π-function. We improve this analysis by applying Strict Avalanche Criterion (SAC) test to ∗ operation and reduced round versions of π-function for π16-Cipher. We obtain that ∗ operation fails SAC test whereas all versions of π-function for π16-Cipher pass the test.


Speaker: Betül Aşkın Özdemir

Title: Statistical Randomness Testing of Some Caesar Candidates Algorithms

Abstract: In order to improve symmetric key research several competitions had arranged by organizations like NIST(National Institute of Standards and Technology) and International Association for Cryptologic Research (IACR). Since the necessity of this kind of security rises, at January 2013, the CAESAR competition announced at the Early Symmetric Crypto workshop. This competition is run by the IACR and this research community will select the final portfolio algorithm. During the competition, a number of algorithms is eliminated in each round. Therefore, the cryptanalysis of algorithms are very important for the CAESAR competition. For this purpose, while the competition continues, we apply cryptographic randomness testing for the algorithms such as Ascon, Morus, Aegis, Pi Cipher, Tiaoxin and Joltik. In this paper, we have focused on the cryptanalysis of the algorithms participated in CAESAR competition using NIST Test Suite. We observe that up to how many rounds, those algorithms, behave random according to NIST Test Suite.



Speaker: Begül Bilgin

Title: Analysing Sbox Properties for Secure and Efficient Implementations

Abstract: The importance of linear and differential properties of an sbox to design cryptographically strong and efficient algorithms has been analysed extensively for the last couple of decades. In this talk, we focus on sbox properties such as decomposability to low-degree functions in order to provide area-efficient and secure implementations. We provide a method that benefits from matrix manipulations and affine equivalence to classify and analyse all quadratic 5-bit permutations and their inverses which can be used for decomposition of any 5-bit permutations. We also introduce an open problem on the existence of an odd quadratic 8-bit permutation together with a clarification of its importance. We then describe how linear properties of coordinate functions of an sbox and their shared component functions can affect the usage of extra randomness for secure implementations against side-channel analysis.


Speaker: Orhun Kara

Title: Cryptanalysis of stream ciphers with keyed update functions

Abstract: We can see that almost all the ultra-lightweight ciphers are block ciphers in the last decade. Block ciphers can achieve a hardware area cost of less than 1k GE whereas one needs almost 1k GE area for a design  of a stream cipher just for its registers so as to resist against tradeoff attacks. One possible method to circumvent the tradeoff attacks without sacrificing the area due to large registers is fixing the key and making use of relatively much smaller internal states. Such ciphers are known as keystream generators with Keyed Update Functions (KUFs). We examine the security status of the keystream generators with KUF in this talk in generic settings. Then we discuss the security of a concrete example.



Speaker: İsa Sertkaya

Title: Security and Privacy Issues in Cloud: Integrity Auditing, Outsourcing Computation, and Secure Deletion

Abstract: Cloud solutions became widely used due to advantage of scalability, accessibility, availability, on demand and pay per usage. However, they also cause loss of control over  the data that would lead to security and privacy issues. In this talk, we first give an overview of cloud computing paradigm, its service and deployment models. Then we summarize a list of security and privacy issues in cloud computing. Finally we dive into cloud specific problems such as privacy preserving remote data integrity checking, outsourcing expensive computation securely, and how to securely delete data from a cloud service provider. Regarding these issues we are going to present our published solutions together with ongoing research results.


Speaker: Aslı Bay

Title: Universal Forgery and Key Recovery Attacks Against  ELmD Authenticated Encryption Algorithm

Abstract: We provide a security analysis of ELmD: a block cipher based Encrypt-Linear-mix-Decrypt authentication mode.

As being one of the second-round CAESAR candidate, it is claimed to provide misuse resistant against forgeries and security against block-wise adaptive adversaries as well as 128-bit security against key recovery attacks.

We scrutinize ElmD in such a way that we provide universal forgery attacks as well as key recovery attacks. Based on the collision attacks on similar structures such as Marble, AEZ, and COPA, we present universal forgery attacks. By exploiting the structure of ELmD, we acquire ability to query to the block cipher inside. For one of the proposed version of ELmD, we mount key recovery attacks reducing the effective key strength by more than 60 bits.



Speaker: Murat Cenk

Title: Fast multiplication algorithms for cryptographic computations

Abstract: Multiplication of big integers and big size polynomials are widely used in various cryptographic schemes. For example, elliptic curve cryptography, finite field cryptography, integer factorization cryptography, and Galois/Counter Mode (GCM) for block ciphers are some of the applications of the fast multiplication algorithms. Since faster algorithms provide more useful systems, much attention has been devoted to develop such algorithms. In this talk, after presenting some of the fast multiplication algorithms, a new efficient method for big integer multiplications will be introduced.