1,238 research outputs found
New Construction of Authentication Codes with Arbitration from Pseudo-Symplectic Geometry over Finite Fields
A new construction of authentication codes with arbitration from
pseudo-symplectic geometry over finite fields is given. The parameters and the
probabilities of deceptions of the codes are also computed.Comment: arXiv admin note: text overlap with arXiv:1302.3160 by other author
The robustness of multiplex networks under layer node-based attack
From transportation networks to complex infrastructures, and to social and
economic networks, a large variety of systems can be described in terms of
multiplex networks formed by a set of nodes interacting through different
network layers. Network robustness, as one of the most successful application
areas of complex networks, has also attracted great interest in both
theoretical and empirical researches. However, the vast majority of existing
researches mainly focus on the robustness of single-layer networks an
interdependent networks, how multiplex networks respond to potential attack is
still short of further exploration. Here we study the robustness of multiplex
networks under two attack strategies: layer node-based random attack and layer
node-based targeted attack. A theoretical analysis framework is proposed to
calculate the critical threshold and the size of giant component of multiplex
networks when a fraction of layer nodes are removed randomly or intentionally.
Via numerous simulations, it is unveiled that the theoretical method can
accurately predict the threshold and the size of giant component, irrespective
of attack strategies. Moreover, we also compare the robustness of multiplex
networks under multiplex node-based attack and layer node-based attack, and
find that layer node-based attack makes multiplex networks more vulnerable,
regardless of average degree and underlying topology. Our finding may shed new
light on the protection of multiplex networks
An efficient dynamic ID based remote user authentication scheme using self-certified public keys for multi-server environment
Recently, Li et al. analyzed Lee et al.'s multi-server authentication scheme
and proposed a novel smart card and dynamic ID based remote user authentication
scheme for multi-server environments. They claimed that their scheme can resist
several kinds of attacks. However, through careful analysis, we find that Li et
al.'s scheme is vulnerable to stolen smart card and offline dictionary attack,
replay attack, impersonation attack and server spoofing attack. By analyzing
other similar schemes, we find that the certain type of dynamic ID based
multi-server authentication scheme in which only hash functions are used and no
registration center participates in the authentication and session key
agreement phase is hard to provide perfect efficient and secure authentication.
To compensate for these shortcomings, we improve the recently proposed Liao et
al.'s multi-server authentication scheme which is based on pairing and
self-certified public keys, and propose a novel dynamic ID based remote user
authentication scheme for multi-server environments. Liao et al.'s scheme is
found vulnerable to offline dictionary attack and denial of service attack, and
cannot provide user's anonymity and local password verification. However, our
proposed scheme overcomes the shortcomings of Liao et al.'s scheme. Security
and performance analyses show the proposed scheme is secure against various
attacks and has many excellent features
A secure and effective anonymous authentication scheme for roaming service in global mobility networks
Recently, Mun et al. analyzed Wu et al.'s authentication scheme and proposed
a enhanced anonymous authentication scheme for roaming service in global
mobility networks. However, through careful analysis, we find that Mun et al.'s
scheme is vulnerable to impersonation attacks, off-line password guessing
attacks and insider attacks, and cannot provide user friendliness, user's
anonymity, proper mutual authentication and local verification. To remedy these
weaknesses, in this paper we propose a novel anonymous authentication scheme
for roaming service in global mobility networks. Security and performance
analyses show the proposed scheme is more suitable for the low-power and
resource-limited mobile devices, and is secure against various attacks and has
many excellent features
A Confident Information First Principle for Parametric Reduction and Model Selection of Boltzmann Machines
Typical dimensionality reduction (DR) methods are often data-oriented,
focusing on directly reducing the number of random variables (features) while
retaining the maximal variations in the high-dimensional data. In unsupervised
situations, one of the main limitations of these methods lies in their
dependency on the scale of data features. This paper aims to address the
problem from a new perspective and considers model-oriented dimensionality
reduction in parameter spaces of binary multivariate distributions.
Specifically, we propose a general parameter reduction criterion, called
Confident-Information-First (CIF) principle, to maximally preserve confident
parameters and rule out less confident parameters. Formally, the confidence of
each parameter can be assessed by its contribution to the expected Fisher
information distance within the geometric manifold over the neighbourhood of
the underlying real distribution.
We then revisit Boltzmann machines (BM) from a model selection perspective
and theoretically show that both the fully visible BM (VBM) and the BM with
hidden units can be derived from the general binary multivariate distribution
using the CIF principle. This can help us uncover and formalize the essential
parts of the target density that BM aims to capture and the non-essential parts
that BM should discard. Guided by the theoretical analysis, we develop a
sample-specific CIF for model selection of BM that is adaptive to the observed
samples. The method is studied in a series of density estimation experiments
and has been shown effective in terms of the estimate accuracy.Comment: 16pages. arXiv admin note: substantial text overlap with
arXiv:1302.393
Charge carrier dynamics in bulk MoS2 crystal studied by transient absorption microscopy
We report a transient absorption microscopy study of charge carrier dynamics
in bulk MoS2 crystals at room temperature. Charge carriers are injected by
interband absorption of a 555-nm pulse, and probed by measuring differential
reflection of a time-delayed and spatially scanned 660-nm pulse. We find an
intervalley transfer time of about 0.35 ps, an energy relaxation time of hot
carriers on the order of 50 ps, and a carrier lifetime of 180 ps. By monitoring
the spatiotemporal dynamics of carriers, we obtained a diffusion coefficient of
thermalized electrons of 4.2 cm2/s, corresponding to a mobility of 170 cm2/Vs.
We also observed a time-varying diffusion coefficient of hot carriers.Comment: 6 pages, 4 figure
Understanding Boltzmann Machine and Deep Learning via A Confident Information First Principle
Typical dimensionality reduction methods focus on directly reducing the
number of random variables while retaining maximal variations in the data. In
this paper, we consider the dimensionality reduction in parameter spaces of
binary multivariate distributions. We propose a general
Confident-Information-First (CIF) principle to maximally preserve parameters
with confident estimates and rule out unreliable or noisy parameters. Formally,
the confidence of a parameter can be assessed by its Fisher information, which
establishes a connection with the inverse variance of any unbiased estimate for
the parameter via the Cram\'{e}r-Rao bound. We then revisit Boltzmann machines
(BM) and theoretically show that both single-layer BM without hidden units
(SBM) and restricted BM (RBM) can be solidly derived using the CIF principle.
This can not only help us uncover and formalize the essential parts of the
target density that SBM and RBM capture, but also suggest that the deep neural
network consisting of several layers of RBM can be seen as the layer-wise
application of CIF. Guided by the theoretical analysis, we develop a
sample-specific CIF-based contrastive divergence (CD-CIF) algorithm for SBM and
a CIF-based iterative projection procedure (IP) for RBM. Both CD-CIF and IP are
studied in a series of density estimation experiments
Efficient laser noise reduction by locking to an actively stabilized fiber interferometer with 10 km arm imbalance
We report a laser noise reduction method by locking it to an actively
stabilized fiber-based Mach Zehnder interferometer with 10 km optical fiber to
achieve large arm imbalance. An acousto optic modulator is used for
interferometer stabilization and heterodyne detection. The out-of-loop
frequency noise is reduced by more than 90 dB for Fourier frequency at 1 Hz.
This structure presents an efficient laser noise reduction method both at high
Fourier frequency and low Fourier frequency. The signal of stabilized laser is
transferred via a 10 km fiber link with a fractional frequency stability of
1.12 times 10-16 at 1 s. Compared with the fractional frequency stability of
that when the interferometer is not stabilized, more than one order of
magnitude is improved.Comment: arXiv admin note: text overlap with arXiv:0901.4856 by other author
Multiple Vectors Propagation of Epidemics in Complex Networks
This letter investigates the epidemic spreading in two-vectors propagation
network (TPN). We propose detailed theoretical analysis that allows us to
accurately calculate the epidemic threshold and outbreak size. It is found that
the epidemics can spread across the TPN even if two sub-single-vector
propagation networks (SPNs) of TPN are well below their respective epidemic
thresholds. Strong positive degree-degree correlation of nodes in TPN could
lead to a much lower epidemic threshold and a relatively smaller outbreak size.
However, the average similarity between the neighbors from different SPNs of
nodes has no effect on the epidemic threshold and outbreak size
Multiple routes transmitted epidemics on multiplex networks
This letter investigates the multiple routes transmitted epidemic process on
multiplex networks. We propose detailed theoretical analysis that allows us to
accurately calculate the epidemic threshold and outbreak size. It is found that
the epidemic can spread across the multiplex network even if all the network
layers are well below their respective epidemic thresholds. Strong positive
degree-degree correlation of nodes in multiplex network could lead to a much
lower epidemic threshold and a relatively smaller outbreak size. However, the
average similarity of neighbors from different layers of nodes has no obvious
effect on the epidemic threshold and outbreak size.Comment: arXiv admin note: substantial text overlap with arXiv:1307.183
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