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

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

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 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