Key recovery attacks on Grain family using BSW sampling and certain weaknesses of the filtering function

A novel internal state recovery attack on the whole Grain family of ciphers is proposed in this work. It basically uses the ideas of BSW sampling along with employing a weak placement of the tap positions of the driving LFSRs. The currently best known complexity trade-offs are obtained, and due to the structure of Grain family these attacks are also key recovery attacks. It is shown that the internal state of Grain-v1 can be recovered with the time complexity of about $2^{66}$ operations using a memory of about $2^{58.91}$ bits, assuming availability of $2^{45}$ keystream sequences each of length $2^{49}$ bits generated for different initial values. Moreover, for Grain-128 or Grain-128a, the attack requires about $2^{105}$ operations using a memory of about $2^{82.59}$ bits, assuming availability of $2^{75}$ keystream sequences each of length $2^{76}$ bits generated for different initial values. These results further show that the whole Grain family, due to the choice of tap positions mainly, does not provide enough security margins against internal state recovery attacks. A simple modification of the selection of the tap positions, as a countermeasure against the attacks described here, is given

Resource Estimation of Grovers-kind Quantum Cryptanalysis against FSR based Symmetric Ciphers

In this paper, we present a detailed study of the cost of the quantum key search attack using Grover. We consider the popular Feedback Shift Register (FSR) based ciphers Grain-128-AEAD, TinyJAMBU, LIZARD, and Grain-v1 considering the NIST\u27s MAXDEPTH depth restriction. We design reversible quantum circuits for these ciphers and also provide the QISKIT implementations for estimating gate counts. Our results show that cryptanalysis is possible with gate count less than $2^{170}$. In this direction, we also study the scenario where initial keystreams may be discarded before using it for encryption so that the Grovers attack on key search becomes costly in terms of circuit repetition. Finally, we connect Grover with BSW sampling for stream ciphers with low sampling resistance. We implement this attack on LIZARD (secret key size of 120 bits, state 121 bits, and security equivalent to 80 bits) and successfully recover the internal states with $2^{40.5}$ queries to the cryptographic oracle and $2^{40}$ amount of data. Our results provide a clear view of the exact status of quantum cryptanalysis against FSR based symmetric ciphers

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Security of Ubiquitous Computing Systems

The chapters in this open access book arise out of the EU Cost Action project Cryptacus, the objective of which was to improve and adapt existent cryptanalysis methodologies and tools to the ubiquitous computing framework. The cryptanalysis implemented lies along four axes: cryptographic models, cryptanalysis of building blocks, hardware and software security engineering, and security assessment of real-world systems. The authors are top-class researchers in security and cryptography, and the contributions are of value to researchers and practitioners in these domains. This book is open access under a CC BY license

Design and Analysis of Cryptographic Pseudorandom Number/Sequence Generators with Applications in RFID

This thesis is concerned with the design and analysis of strong de Bruijn sequences and span n sequences, and nonlinear feedback shift register (NLFSR) based pseudorandom number generators for radio frequency identification (RFID) tags. We study the generation of span n sequences using structured searching in which an NLFSR with a class of feedback functions is employed to find span n sequences. Some properties of the recurrence relation for the structured search are discovered. We use five classes of functions in this structured search, and present the number of span n sequences for 6 <= n <= 20. The linear span of a new span n sequence lies between near-optimal and optimal. According to our empirical studies, a span n sequence can be found in the structured search with a better probability of success. Newly found span n sequences can be used in the composited construction and in designing lightweight pseudorandom number generators. We first refine the composited construction based on a span n sequence for generating long de Bruijn sequences. A de Bruijn sequence produced by the composited construction is referred to as a composited de Bruijn sequence. The linear complexity of a composited de Bruijn sequence is determined. We analyze the feedback function of the composited construction from an approximation point of view for producing strong de Bruijn sequences. The cycle structure of an approximated feedback function and the linear complexity of a sequence produced by an approximated feedback function are determined. A few examples of strong de Bruijn sequences with the implementation issues of the feedback functions of an (n+16)-stage NLFSR are presented. We propose a new lightweight pseudorandom number generator family, named Warbler family based on NLFSRs for smart devices. Warbler family is comprised of a combination of modified de Bruijn blocks (CMDB) and a nonlinear feedback Welch-Gong (WG) generator. We derive the randomness properties such as period and linear complexity of an output sequence produced by the Warbler family. Two instances, Warbler-I and Warbler-II, of the Warbler family are proposed for passive RFID tags. The CMDBs of both Warbler-I and Warbler-II contain span n sequences that are produced by the structured search. We analyze the security properties of Warbler-I and Warbler-II by considering the statistical tests and several cryptanalytic attacks. Hardware implementations of both instances in VHDL show that Warbler-I and Warbler-II require 46 slices and 58 slices, respectively. Warbler-I can be used to generate 16-bit random numbers in the tag identification protocol of the EPC Class 1 Generation 2 standard, and Warbler-II can be employed as a random number generator in the tag identification as well as an authentication protocol for RFID systems.1 yea

Addressing subjectivity in the classification of palaeoenvironmental remains with supervised deep learning convolutional neural networks

Archaeological object identifications have been traditionally undertaken through a comparative methodology where each artefact is identified through a subjective, interpretative act by a professional. Regarding palaeoenvironmental remains, this comparative methodology is given boundaries by using reference materials and codified sets of rules, but subjectivity is nevertheless present. The problem with this traditional archaeological methodology is that higher level of subjectivity in the identification of artefacts leads to inaccuracies, which then increases the potential for Type I and Type II errors in the testing of hypotheses. Reducing the subjectivity of archaeological identifications would improve the statistical power of archaeological analyses, which would subsequently lead to more impactful research. In this thesis, it is shown that the level of subjectivity in palaeoenvironmental research can be reduced by applying deep learning convolutional neural networks within an image recognition framework. The primary aim of the presented research is therefore to further the on-going paradigm shift in archaeology towards model-based object identifications, particularly within the realm of palaeoenvironmental remains. Although this thesis focuses on the identification of pollen grains and animal bones, with the latter being restricted to the astragalus of sheep and goats, there are wider implications for archaeology as these methods can easily be extended beyond pollen and animal remains. The previously published POLEN23E dataset is used as the pilot study of applying deep learning in pollen grain classification. In contrast, an image dataset of modern bones was compiled for the classification of sheep and goat astragali due to a complete lack of available bone image datasets and a double blind study with inexperienced and experienced zooarchaeologists was performed to have a benchmark to which image recognition models can be compared. In both classification tasks, the presented models outperform all previous formal modelling methods and only the best human analysts match the performance of the deep learning model in the sheep and goat astragalus separation task. Throughout the thesis, there is a specific focus on increasing trust in the models through the visualization of the models’ decision making and avenues of improvements to Grad-CAM are explored. This thesis makes an explicit case for the phasing out of the comparative methods in favour of a formal modelling framework within archaeology, especially in palaeoenvironmental object identification

Alternative Energy Sources

The search for alternative sources of energy is an attempt to solve two of the main problems facing the modern world. Today's resources are mainly based on fossil flammable substances such as coal, oil, and natural gas. The first problem is related to the expected and observed depletion of deposits, not only those available but also less accessible. Another is related to global warming from emissions of greenhouse gases (mainly carbon dioxide) as well as emissions of other pollutants in the atmosphere. Mitigating the harmful effects of fossil fuel use is an obvious challenge for mankind. This Special Issue includes articles on the search for new raw materials and new technologies for obtaining energy, such as those existing in nature, methane hydrates, biomass, etc., new more efficient technologies for generating electricity, as well as analyses of the possibilities and conditions of use of these resources for practical applications

Stress-strain characteristics of rockfill, and of clays under high pore water tension

Imperial Users onl

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids