Cryptanalysis of two chaotic encryption schemes based on circular bit shift and XOR operations

Recently two encryption schemes were proposed by combining circular bit shift and XOR operations, under the control of a pseudorandom bit sequence (PRBS) generated from a chaotic system. This paper studies the security of these two encryption schemes and reports the following findings: 1) there exist some security defects in both schemes; 2) the underlying chaotic PRBS can be reconstructed as an equivalent key by using only two chosen plaintexts; 3) most elements in the underlying chaotic PRBS can be obtained by a differential known-plaintext attack using only two known plaintexts. Experimental results are given to demonstrate the feasibility of the proposed attack.Comment: 17 pages, 8 figure

Discontinuity of Maximum Entropy Inference and Quantum Phase Transitions

In this paper, we discuss the connection between two genuinely quantum phenomena --- the discontinuity of quantum maximum entropy inference and quantum phase transitions at zero temperature. It is shown that the discontinuity of the maximum entropy inference of local observable measurements signals the non-local type of transitions, where local density matrices of the ground state change smoothly at the transition point. We then propose to use the quantum conditional mutual information of the ground state as an indicator to detect the discontinuity and the non-local type of quantum phase transitions in the thermodynamic limit.Comment: Major revision. 26 pages, 12 figure

Model Extraction Attack against Self-supervised Speech Models

Self-supervised learning (SSL) speech models generate meaningful representations of given clips and achieve incredible performance across various downstream tasks. Model extraction attack (MEA) often refers to an adversary stealing the functionality of the victim model with only query access. In this work, we study the MEA problem against SSL speech model with a small number of queries. We propose a two-stage framework to extract the model. In the first stage, SSL is conducted on the large-scale unlabeled corpus to pre-train a small speech model. Secondly, we actively sample a small portion of clips from the unlabeled corpus and query the target model with these clips to acquire their representations as labels for the small model's second-stage training. Experiment results show that our sampling methods can effectively extract the target model without knowing any information about its model architecture

Weekday effects on gold: Tokyo, London, and New York markets

Using the probability distribution approach, this study explores the weekday effects among Tokyo, London, and New York gold markets. Friday shows positive and significant higher returns, whereas Tuesday shows negative and significant lower returns than other weekdays. The weekend effects still exist, while Monday effects disappear. On average, London was found to have the highest returns, followed by New York and Tokyo. The peak and width estimations show that Tokyo has the highest volatility, while London and New York have similar volatility distributions, implying a similar preference behavior of investors. It also implies that arbitrage opportunities between London and New York could be trivial. After estimating the distribution from Monday to Friday across the three markets, we found that the distribution of return shows a leftward shifting in London and New York, meaning that the weekend effect is starting earlier from Wednesday and Thursday in London and New York. Some strategy implications are valuable to traders or hedgers Vol. 11, Iss: 2, pp.33-44

Growth and properties of few-layer graphene prepared by chemical vapor deposition

The structure, and electrical, mechanical and optical properties of few-layer graphene (FLG) synthesized by chemical vapor deposition (CVD) on a Ni coated substrate were studied. Atomic resolution transmission electron microscope (TEM) images show highly crystalline single layer parts of the sample changing to multilayer domains where crystal boundaries are connected by chemical bonds. This suggests two different growth mechanisms. CVD and carbon segregation participate in the growth process and are responsible for the different structural formations found. Measurements of the electrical and mechanical properties on the centimeter scale provide evidence of a large scale structural continuity: 1) in the temperature dependence of the electrical conductivity, a non-zero value near 0 K indicates the metallic character of electronic transport; 2) the Young's modulus of a pristine polycarbonate film (1.37 GPa) improves significantly when covered with FLG (1.85 GPa). The latter indicates an extraordinary Young modulus value of the FLG-coating of TPa orders of magnitude. Raman and optical spectroscopy support the previous conclusions. The sample can be used as a flexible and transparent electrode and is suitable for special membranes to detect and study individual molecules in high resolution TEM