Wyniki wyszukiwania - BazTech

1

Attribute-based Data Integrity Checking for Cloud Storage

Tian M., Wang L., Zhong H., Chen J.

Fundamenta Informaticae

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2018

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Vol. 163, nr 4

395--411

EN

Cloud storage is a significant service provided by the cloud that enables users to store their immense data into the cloud. As the advent of the big data era, cloud storage services are becoming increasingly popular. For security reasons, data owners would like to check the integrity of their data after storing it in the cloud. To do this, they usually make use of the public cloud data integrity checking schemes. This paper focuses on user anonymity in such schemes so that no third party could infer the identity information of any data owner from checking procedures. The problem is obviously inevitable in reality, however the current solutions are relatively involved as they heavily use public key certificates and/or incur huge communication overhead. In this paper we introduce the concept of attribute-based cloud data integrity checking to achieve user anonymity lightly and present security models for such systems. We also provide a practical construction and prove its security in the random oracle model. Finally, we show how to extend our construction to protect data privacy against any third party.

2

Curvelet-domain multiple matching method combined with cubic B-spline function

Wang T., Wang D., Tian M., Hu B., Liu C.

Acta Geophysica

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2018

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Vol. 66, no. 4

559--573

EN

Since the large amount of surface-related multiple existed in the marine data would influence the results of data processing and interpretation seriously, many researchers had attempted to develop effective methods to remove them. The most successful surface-related multiple elimination method was proposed based on data-driven theory. However, the elimination effect was unsatisfactory due to the existence of amplitude and phase errors. Although the subsequent curveletdomain multiple–primary separation method achieved better results, poor computational efficiency prevented its application. In this paper, we adopt the cubic B-spline function to improve the traditional curvelet multiple matching method. First, select a little number of unknowns as the basis points of the matching coefficient; second, apply the cubic B-spline function on these basis points to reconstruct the matching array; third, build constraint solving equation based on the relationships of predicted multiple, matching coefficients, and actual data; finally, use the BFGS algorithm to iterate and realize the fast-solving sparse constraint of multiple matching algorithm. Moreover, the soft-threshold method is used to make the method perform better. With the cubic B-spline function, the differences between predicted multiple and original data diminish, which results in less processing time to obtain optimal solutions and fewer iterative loops in the solving procedure based on the L1 norm constraint. The applications to synthetic and field-derived data both validate the practicability and validity of the method.

3

Inverse data-space multiple elimination with 3D curvelet sparsity promotion

Wang T., Wang D., Wang T., Tian M.

Acta Geophysica

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2017

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Vol. 65, no. 6

1197--1205

EN

This paper describes an effective implementation of the inverse data-space multiple elimination method via the three-dimensional (3D) curvelet domain. The method can separate the surface-related operator (A) and primaries (P0) through seismic data matrix inversion. A 3D curvelet transform is introduced to sparsely represent the seismic data in the inverse data space. Hence, this approach is suitable for obtaining an accurate solution because of its multiscale and multidirectional analysis properties. The L1 norm is used to promote sparseness in the transform domain. Then, a high-fidelity separation of the operator (A) and the primaries (P0) is realized. The proposed method is applied to synthetic data from a model containing a salt structure. We compare the results with that of the traditional inverse data-space multiple elimination method and also with that of two-dimensional surface-related multiple elimination. The findings fully demonstrate the superiority of the proposed method over the traditional inverse method; moreover, the proposed method protects the primary energy more effectively than the SRME method.

4

Identity-based Signatures from Lattices : Simpler, Faster, Shorter

Tian M., Huang L.

Fundamenta Informaticae

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2016

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Vol. 145, nr 2

171--187

EN

Identity-based signature is an important technique for light-weight authentication. Recently, many efforts have been made to construct identity-based signatures over lattice assumptions since they would remain secure in future quantum age. In this paper we present a new identitybased signature scheme from lattice problems. This scheme is more efficient than other lattice-based identity-based signature schemes in terms of both computation and communication complexities. We prove its security in the random oracle model under short integer solution assumption that is as hard as approximating several worst-case lattice problems. We also extend the scheme to an identity-based message recovery signature scheme that has better performance.

5

Cryptanalysis and Improvement of a Certificateless Multi-proxy Signature Scheme

Tian M., Yang W., Huang L.

Fundamenta Informaticae

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2014

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Vol. 129, nr 4

365--375

EN

Certificateless cryptography is a new type of public key cryptography,which removes the certificate management problem in traditional public key cryptography and the key escrow problem in identity-based public key cryptography. Multi-proxy signature is an extension of proxy signature, which allows an original signer authorizing a group of proxy signers and only the cooperation of all proxy signers in the group can create valid proxy signatures on behalf of the original signer. Recently, Jin andWen combined certificateless cryptographywith multi-proxy signature, and proposed a model as well as a concrete scheme of certificateless multi-proxy signature. They claimed that their scheme is provably secure in their security model. Unfortunately, in this paper by giving two attacks, we will show that their certificateless multi-proxy signature scheme can be broken. The first attack indicates their security model is flawed and the second attack indicates their certificateless multi-proxy signature scheme is insecure. Possible improvements are also suggested to prevent these attacks.

6

Preparation and Properties of Natural Cellulose Fibres from

Qu L, Tian M., Guo X., Pan N, Zhang X., Zhu S

Fibres & Textiles in Eastern Europe

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2014

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Vol. 22, no. 4 (106)

24--28

EN

Natural cellulose fibres from Broussonetia papyrifera (L.) Vent. (BP) bast were systematically investigated in this paper. To begin with, BP fibres were successively extracted from BP bast by four different degumming methods, among which the microwave-assisted method exhibited high efficiency. It was found that non-cellulose substances were sufficiently removed or reduced after the degumming process, but the cellulose I structure had not changed from bast to fibres based on the XRD and FTIR results. Meanwhile the BP fibres exhibited high crystallinity (75 ~ 77%), high breaking strength (2.19 ~ 2.39 cN/dtex) and a remarkable moisture region (6.3 ~ 8.7%), but low breaking elongation (1.0 ~ 2.1%). All those results indicated that the BP fibres had properties resembling those of traditional natural cellulose fibres (e.g. cotton and flax); therefore they could be viewed as a promising alternative source for natural cellulose bundle fibres.

PL

Artykuł poświecono systematycznym badaniom naturalnych włókien celulozowych z Broussonetia Papyrifera (BP). Włókna ekstrahowano z włókien łykowych BP poprzez 4 rożne metody odpreparowania pomiędzy z których metoda za pomocą zastosowania ultradźwięków pozwoliła na uzyskanie wysokiej wydajności. Stwierdzono, że nie celulozowe substancje były dostatecznie usunięte lub zredukowane po procesie odpreparowania. Dzięki badaniom XRD i FITR można było wykazać, że struktura celulozy (I) nie zmieniła się pomiędzy włóknami łykowymi i otrzymanymi z nich wyrobami. dalsze badania wykazały źe włókna BP maja wysoką krystaliczność (75 - 77%), wysoką wytrzymałość(2.19 - 2.39 cN/dtex) i znaczną pochłanialność wilgoci (6.3 - 8.7%) natomiast małe wydłużenie przy zerwaniu (1.0 - 2.1%). Wszystkie te wyniki wskazują,że włókna BP posiadają właściwości przypominające właściwości tradycyjnych, naturalnych włókien celulozowych (np. bawełny i lnu). Dlatego też badane włok-na można uważać jako alternatywne źródło naturalnych włókien celulozowych.

7

A facile synthesizing method of vanadium dioxide by pyrolyzing ammonium metavanadate

Qi J., Ning G., Hua R., Tian M., Liu S.

Materials Science Poland

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2012

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Vol. 30, No. 2

151--157

EN

A facile process was developed for synthesizing vanadium dioxide (VO2) by pyrolyzing ammonium metavanadate (NH4VO3) in nitrogen flow. The process was designed on the base of thermodynamic modeling of chemical reaction and thermal analyzing of NH4VO3 pyrogenation in N2 gas, and optimized by experiments. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were applied to characterizing the product VO2. Thermo-gravimetric analysis (TG) and DSC were used for analyzing the process of NH4VO3 pyrogenation. The experimental results indicated that VO2 microcrystal particles were successfully synthesized. The product VO2 presents two kinds of micro morphologies, torispherical and pentagonal prism. The phase transition mainly takes place at 338.4 K and 341.9 K. The average enthalpy of the phase transition is 28.82 J/g.

8

Optimum separation condition of five bioactive compounds by HCI program in HPLC

Tian M., Li S., Row K. H.

Acta Chromatographica

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2012

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Vol. 24, no. 1

65--74

EN

An efficient method used to separate five bioactive compounds from Gelidium amansii was optimized by the HCI software. The optimum composition of mobile phase for high-performance liquid chromatographic (HPLC) separation was obtained. The elution profiles were calculated by the polynomial theory based on the retention factor ln k = A + BF + CF2 (F was the volume percentage of acetonitrile with 1.0% acetic acid); then, the theory was applied to calculate the elution profile in both isocratic and gradient modes by modifying different mobile phase conditions with HCI program. The calculated results of mobile phase condition suggested that acetonitrile-water (containing 1.0% acetic acid) with a linear gradient elution of 0∼30 min from 15:85 to 50:50 (v/v) was the optimized component. In the experimental conditions, the agreement between the experimental elution profiles and the calculated values of eluted concentration was relatively good.

9

Synthesis and characterization of V2O3 microcrystal particles controlled by thermodynamic parameters

Qi J., Ning G., Zhao Y., Tian M., Xu Y., Hai H.

Materials Science Poland

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2010

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Vol. 28, No. 2

535--543

EN

A facile process is developed for the synthesis of pure vanadium(III) oxide by thermal reduction of vanadium pentoxide (V2O5) in ammonia gas. The process of thermal reduction of V2O5 was optimized by experiments and by modeling of thermodynamic parameters. The obtained V2O3 was characterized by X-ray diffraction, X-ray photoelectron spectrometry, scanning electron microscopy and thermogravimetric analysis. The experimental results indicated that crystal particles of pure V2O3 were successfully synthesized within a short reaction period of 1 h and at a relatively low temperature of 903 K. The content of V2O3 in the product sample higher than 99 wt. %. The grain size of V2O3 ranged from several hundred nanometers to several micrometers. The morphologies of the V2O3 particles were micrometer layers in nanometer sheet structure.

10

Preparation and characterization of La- and Ni-doped magnetite nanoparticles

Ma J., Ji Y., Tian M.

Materials Science Poland

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2009

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Vol. 27, No. 4/1

981--986

EN

La- and Ni-doped Fe3O4 nanocomposite particles with a high saturation magnetization were prepared by a homogeneous precipitation method in aqueous solutions. The obtained nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively-coupled plasma atomic emission spectroscopy (ICPAES) and vibrating sample magnetometry (VSM). The results showed the diameters of La- or Ni-doped Fe3O4 composite particles to be in the range of 10-25 nm. The specific saturation magnetization of La- or Ni-doped Fe3O4 was considerably higher than that of pure Fe3O4 nanoparticles. The nanocomposite particles exhibited superparamagnetic behaviour.