Search results for "Crypt"

M-Centrality: identifying key nodes based on global position and local degree variation

2023

Identifying influential nodes in a network is a major issue due to the great deal of applications concerned, such as disease spreading and rumor dynamics. That is why, a plethora of centrality measures has emerged over the years in order to rank nodes according to their topological importance in the network. Local metrics such as degree centrality make use of a very limited information and are easy to compute. Global metrics such as betweenness centrality exploit the information of the whole network structure at the cost of a very high computational complexity. Recent works have shown that combining multiple metrics is a promising strategy to quantify the node's influential ability. Our wor…

New adaptive synchronization algorithm for a general class of complex hyperchaotic systems with unknown parameters and its application to secure comm…

2022

Abstract The aim of this report is to investigate an adaptive synchronization (AS) for the general class of complex hyperchaotic models with unknown parameters and a new algorithm to achieve this type of synchronization is proposed. Owing to the intricacy behavior of hyperchaotic models that could be effective in secure communications, the special control based on adaptive laws of parameters is constructed analytically, and the corresponding simulated results are performed to validate the algorithm’s accuracy. The complex Rabinovich model is utilized as an enticing example to examine the proposed synchronization technique. A strategy for secure communication improving the overall cryptosyst…

The in, out Asymmetric Pseudo-Triple Helical Form of a D3h Diaza-Macropentacycle

2007

A sterically encumbered [N(2)S(6)] macropentacycle (5) related to diazamacrobicycles and cryptands has been synthesized in 53% yield by the [1+1] condensation reaction between functionalized macrocyclic and macrotricyclic precursors. A macrononacycle (18) resulting from the corresponding [2+2] condensation was isolated in 7% yield from the reaction mixture. Both compounds showed broad features in their room-temperature (1)H NMR spectra, but their maximal average symmetry (D(3h) and D(2h), respectively) was achieved at high temperature (380 K). At low temperature (200 K, CD(2)Cl(2) solution), the macropentacycle is "frozen" to a single asymmetric (C1) conformation on the (1)H NMR time scale,…

THE KEY ROLE OF LIQUIDITY FLUCTUATIONS IN DETERMINING LARGE PRICE CHANGES

2005

Recent empirical analyses have shown that liquidity fluctuations are important for understanding large price changes of financial assets. These liquidity fluctuations are quantified by gaps in the order book, corresponding to blocks of adjacent price levels containing no quotes. Here we study the statistical properties of the state of the limit order book for 16 stocks traded at the London Stock Exchange (LSE). We show that the time series of the first three gaps are characterized by fat tails in the probability distribution and are described by long memory processes.

Talking Blockchains: The Perspective of a Database Researcher

2021

There are few topics out there, that seem to create as much confusion and discussion as blockchains. This has a multitude of reasons: (1) A large number of drastically different concepts and systems are unified under the very broad term "blockchain". (2) The topic touches a variety of different fields, including databases, distributed processing, networks, cryptography, and even economics. (3) There exists a large number of different applications of the technology.The goal of this paper is to simplify and structure the discussion of blockchain technology. We first introduce a simple formalization of the basic components, that appear again and again in a variety of blockchain systems. Second…

Traceable hierarchical attribute-based authentication for the cloud

2015

When data owners store their data on cloud servers, they may want to define the access requirements themselves, where attribute-based authentication (ABA) can be a good choice for the solution. In this paper, we propose a traceable hierarchical ABA (HABA) solution which fits two situations in the cloud. The first situation is when cloud users are organized in groups of a hierarchical structure and the access allowance can only be granted to users in a specific group. The second situation is that attributes are organized in a hierarchical structure with different priorities, such that only users who own the required attributes of a specific priority can be authenticated and access the data. …

2015

Abstract. The coupling of Earth system model components, which work on different grids, into an Earth System Model (ESM) provokes the necessity to transfer data from one grid to another. Additionally, each of these model components might require data import onto its specific grid. Usually, one of two approaches is used: Either all input data is preprocessed to the employed grid, or the imported data is interpolated on-line, i.e. during model integration to the required grid. For the former, each change in the model resolution requires the re-preprocessing of all data. The latter option implies that in each model integration computing time is required for the grid mapping. If all components …

Optimal Adaptive Inspection Planning Process in Service of Fatigued Aircraft Structures

2009

In this paper, a control theory is used for planning inspections in service of fatigue-sensitive aircraft structure components under crack propagation. One of the most important features of control theory is its great generality, enabling one to analyze diverse systems within one unified framework. A key idea, which has emerged from this study, is the necessity of viewing the process of planning in-service inspections as an adaptive control process. Adaptation means the ability of self-modification and self-adjustment in accordance with varying conditions of environment. The adaptive control of inspection planning process in service of fatigued aircraft structures differs from ordinary stoc…

Applying Finite State Process Algebra to Formally Specify a Computational Model of Security Requirements in the Key2phone-Mobile Access Solution

2015

Key2phone is a mobile access solution which turns mobile phone into a key for electronic locks, doors and gates. In this paper, we elicit and analyse the essential and necessary safety and security requirements that need to be considered for the Key2phone interaction system. The paper elaborates on suggestions/solutions for the realisation of safety and security concerns considering the Internet of Things (IoT) infrastructure. The authors structure these requirements and illustrate particular computational solutions by deploying the Labelled Transition System Analyser (LTSA), a modelling tool that supports a process algebra notation called Finite State Process (FSP). While determining an in…

ASR in Classroom Today : Automatic Visualization of Conceptual Network in Science Classrooms

2017

Automatic Speech Recognition (ASR) field has improved substantially in the last years. We are in a point never saw before, where we can apply such algorithms in non-ideal conditions such as real classrooms. In these scenarios it is still not possible to reach perfect recognition rates, however we can already take advantage of these improvements. This paper shows preliminary results using ASR in Chilean and Finnish middle and high school to automatically provide teachers a visualization of the structure of concepts present in their discourse in science classrooms. These visualizations are conceptual networks that relate key concepts used by the teacher. This is an interesting tool that gives…