# Róbert Lórencz's research while affiliated with Czech Technical University in Prague and other places

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## Publications (42)

In this paper we propose a set of algorithms that can automatically detect the use of AES and automatically recover both the encryption key and the plaintext, assuming that we can control the code flow of the encrypting program, e.g., when an application is performing encryption without the user’s permission. The first algorithm makes use of the fa...

This work presents new advances in algebraic cryptanalysis of small scale derivatives of AES. We model the cipher as a system of polynomial equations over GF(2), which involves only the variables of the initial key, and we subsequently attempt to solve this system using Gröbner bases. We show, for example, that one of the attacks can recover the se...

This paper investigates the behaviour of the Physical Unclonable Function (PUF) design proposed in our previous work that is based ring oscillators (ROs). Our approach is able to extract multiple output bits from each RO pair in contrary to the classical approach, where frequencies of ROs are compared. We study the behaviour of our PUF design toget...

The goal of distance metric learning is to find the most appropriate distance metric parameters to improve similarity-based models such as k-Nearest Neighbors or k-Means. In this paper, we apply distance metric learning to the problem of malware detection.We focus on two tasks: (1) to classify malware and benign files with a minimal error rate, (2)...

The goal of distance metric learning is to find the most appropriate distance metric parameters to improve similarity-based models, such as k-Nearest Neighbors or k-Means. In this paper, we applied distance metric learning for the problem of malware detection. We focused on two tasks: (1) to classify malware and benign files with a minimal error ra...

Distance metric learning is concerned with finding appropriate parameters of distance function with respect to a particular task. In this work, we present a malware detection system based on static analysis. We use k-nearest neighbors (KNN) classifier with weighted heterogeneous distance function that can handle nominal and
numeric features extract...

Classification of automatically generated malware is an active research area. The amount of new malware is growing exponentially, and since manual investigation is not possible, automated malware classification is necessary. This paper presents a static malware detection system for detecting unknown malicious programs based on the weighted k-neares...

In this paper we propose the method of generating true random numbers utilizing the circuit primarily designed as Physically Unclonable Function (PUF) based on ring oscillators. The goal is to show that it is possible to design the universal crypto system, that can be used for various applications - the PUF can be utilized for asymmetric cryptograp...

This paper is focused on error-free solution of dense linear systems using residual arithmetic in hardware. The designed Modular System uses hardware identical Residual Processors (RP)s for solving independent systems of linear congruences and combines their solutions into the solution of the given linear system. This approach uses the residue numb...

PUFs (Physical Unclonable Function) are increasingly used in proposals of security architectures for device identification and cryptographic key generation. Many PUF designs for FPGAs proposed up to this day are based on ring oscillators (RO). The classical approach is to compare frequencies of ROs and produce a single output bit from each pair of...

This paper deals with design of physical unclonable functions (PUFs) based on field-programmable gate array (FPGA). The goal was to propose a cheap, efficient and secure device identification or even a cryptographic key generation based on PUFs. Therefore, a design of a ring oscillator (RO)-based PUF producing more output bits from each RO pair is...

We present results of linear cryptanalysis of Baby Rijndael, a reduced-size model of Rijndael. The results were obtained using exhaustive search of all approximations and all keys and show some curious properties of both linear cryptanalysis and Baby Rijndael, particularly the existence of different classes of linear approximations with significant...

Nowadays the security becomes more and more important and as a need for secure data encryption grows, we have to be sure that the algorithms we are using are safe. But it is not always just about algorithm itself as about settings, for example key length. RSA, the most popular asymmetric cipher is a perfect example, because it fully depends on hard...

The paper describes an ASIC implementation of a previously implemented FPGA linear congruence solver, part of a parallel system for solution of linear equations, and presents synthesis results for three different standard cell libraries. The previous VHDL design was adapted to three ASIC technologies (130 nm, 110 nm, and 55 nm) from two different v...

This paper is focused on hardware error-free solution of dense linear systems using residual arithmetic on a System on Chip Modular System. The designed Modular System uses Residual Processors (RP)s for solving independent linear systems in residue arithmetic and combines RP solutions into solution of the linear system. In order to efficiently expl...

Residual processor (RP) is a dedicated hardware for solution of sets of linear congruences. RPs are parts of a larger modular system for error-free solution of linear equations in residue arithmetic. We present new FPGA and ASIC RP implementations, focusing mainly on their memory units being a bottleneck of the calculation and therefore determining...

The paper first describes an existing parameter estimation approach used to estimate MOSFET mathematical model parameters. Next, all of the presented algorithms are analyzed with respect to the current multiple core processor architecture design. The parallel equivalents of the presented algorithms are given, including their computational complexit...

We present the hardware architecture of an arithmetic unit intended for computing basic operations over a Galois field GF(p). The arithmetic unit supports addition, subtraction, multiplication, and multiplicative inverse modulo a prime p. To compute the multiplicative inverse, we use the promising left-shifting algorithm that is based on the extend...

The residual processor is a dedicated hardware for solving sets of linear congruences. It is a part of the modular system for solving sets of linear equations without rounding errors using Residue Number System. We present a new FPGA implementation of the residual processor, focusing mainly on the memory unit that forms a bottleneck of the calculat...

We present a method of generating true random numbers on an Atmel AVR microcontroller. The jitter of the built-in RC oscillator is used as the source of entropy to generate 8 random bits per second. When implemented on the AVR Butterfly demo board, our method needs no external components; otherwise, only an external oscillator is needed. We tested...

ProTools, an industry standard audio edit and mix software, is not accessible for visually impaired. Precisely, it was not accessible and this paper presents how was ProTools access enabled with the help of ProAccess application. ProAccess was created for this purpose and uses mach code injection techniques to load an access enabling bundle into Pr...

Apple Human Interface Guidelines state that all applications should be accessible in order to provide the best user experience.
Not all software vendors honor this statement and if an application does not support accessibility, people with disability
or a special need can hardly use it or cannot use it at all. The purpose of this paper is to presen...

We introduce architecture of an arithmetic unit that is based on continued fractions and allows computing any linear rational function of two variables, including basic arithmetic operations like addition, subtraction, multiplication and division. Such a unit can easily exploit the parallel nature of continued fraction arithmetic and accelerate the...

This paper presents FPGA implementations of traditional almost Montgomery inverse and subtraction-free almost Montgomery inverse and compares their space and time properties. The subtraction-free algorithm with its hardware architecture overcomes the disadvantages of currently known methods (e.g. Gutub, et al., 2002). The ">" or "<" tests that requ...

A new modification of Kaliski's algorithm for computing the Almost Montgomery Inverse, optimized for implementation in hardware, is presented. The algorithm and the corresponding portion of the hardware architecture overcome certain drawbacks of the currently used methods. In particular, the “less than/greater than” tests that represent subtraction...

In this paper, we discuss the options for brute-force cracking of the RC5 block cipher, that is, for revealing the unknown secret key, given a sample ciphertext and a portion of the corresponding plaintext. First, we summarize the methods employed by the current cracking efforts. Then, we present two hardware architectures for finding the secret ke...

The Montgomery inverse is used in cryptography for the computation of modular inverse of 6 modulo a, where a is a prime. We analyse existing algorithms from the point of view of their hardware implementation. We propose a new, hardware-optimal algorithm for the calculation of the classical modular inverse. The left-shift binary algorithm is shown t...

The Montgomery inverse is used in cryptography for the computation of modular inverse of b modulo a, where a is a prime. We analyse existing algorithms from the point of view of their hardware implementation. We propose a new, hardware-optimal algorithm for the calculation of the classical modular inverse. The left-shift binary algorithm is shown t...

## Citations

... Extensions to these models are discussed in [21,22,23], wherein researchers have proposed use of Lightweight Convolutional Neural Networks (LCNN), Soft Relevance Evaluation (SRE), and Error Correction Output Coding (ECOC) with Transfer Learning (TL), which assist in lowerror and high accuracy classification operations. Extensions to these models are discussed in [24,25,26,27], which utilize CNN with 10-fold cross-validation (CV), Particle Swarm Optimization (PSO) with k Nearest Neighbours (kNN), CNN, and Enhanced Stacking Ensemble Framework (eSEM) with Multi-Layer Perception (MLP), Principal Component Analysis (PCA) and Support Vector Machine (SVM) for classification of context-specific malware types. But these models do not allow for localization of malwares, which limits their applicability for real-time environments. ...

... For computation of the energy cost of encryption, by using the cycles, the operating voltage of the CPU, and the average current drawn for each cycle, we can calculate the energy consumption of cryptographic functions [13]. More modern encryption algorithms were developed from 1990s IDEA RC5 [10], RC6 followed in new millennium UMARAM [12] and UR5 with new algorithm structure and are listed in Table 3: ...

Reference: GDPR COMPLIANT METHODS OF DATA PROTECTION

... The Microsoft domain environment is one of the most critical systems in a corporate network [1]. The Windows domain directory services implementation known as Active Directory (AD) is used to offer services for user and identity management, authentication, and policy administration. ...

... Malware detection can be defined as a classification problem with two classes: malware and benign samples. The more challenging problem is to cluster malware into malware families [5]. In this work, we empirically demonstrate how to apply distance metric learning to malware detection using a KNN classifier. ...

... Since the process deviation in different chips is completely random, the generated challenge-response relationship is also unique. PUF has multiple characteristics such as unclonability, uniqueness, unpredictability, light weight and tamper resistance, so it is used in multiple hardware security fields such as identity authentication [1,2], implementation of property rights protection [3,4], key generation [5,6], and device authentication [7]. Since the concept of physical unclonable function was first proposed in 2002 [8], delay-based PUF such as arbiter PUF [9], ring oscillator(RO) PUF [10,11,12], glitch PUF [13] and storage-based PUF such as SRAM PUF [3], butterfly PUF [14], latch PUF [15] and flip-flop PUF [16] have also been proposed. ...

... This paper can be considered as an extension of them. In [27], we applied the Particle Swarm Optimization algorithm to the problem of finding the appropriate feature weights used in the heterogeneous distance function [28] specifically defined for the PE file format to classify malware and benign files. We showed that the error rate of the KNN classifier could be decreased by 12.77 % using the weighted distance function. ...

... Many cryptanalysts proved that due to weaknesses of this stream cipher, information security can be compromised in GSM [25,28,29]. These weaknesses are: ...

... Gerçek rastgele sayı üreteçleri (GRSÜ) genellikle gerçek bir sinyale dayalı olarak tasarlanan sayı üreteçlerine verilen isimdir. Sözde rastgele sayı üreteçleri (SRSÜ) ise çeşitli algoritmalar yardımıyla herhangi bir gerçek sinyale bağlı kalmadan gerçekleştirilen sayı üreteçleridir [1], [2]. ...

... Otherwise, it will work as a buffer with a challenge bit 0. Liu et al. proposed a PUF in [37] which is re-configurable based on the challenge input. Simona et al. [38] presented a TRNG which is based on ROPUF. The core building component of the TRNG is the five-stage ring oscillator. ...

... This handicap is partially alleviated in the RO-PUF proposed in [17,18], which allows 127 more than one bit to be added to the PUF response for each comparison. Unlike the 128 conventional proposal in which the counting interval is fixed by an external clock, in this 129 case, the decision is taken when the counter of the faster RO overflows. ...