3,731 research outputs found
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
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