Abstract:Vertex cover problem is a classical NP complete problem,which has many applications in areas of sorting,computer network,etc.In recent years,many researchers begin to explore its generalized form,namely vertex cover P_k problem,which requires to find a subset of vertices such that the induced subgraphs by the rest vertices of the topological structure do not include any P_k path,where P_k is the path on k vertices.This paper firstly introduces the application background of vertex cover P_k problem,then summarizes current researches in approximation algorithms,exact algorithms and parameter algorithms,and analyzes some commonly used methods and techniques.On this basis,we point out the direction for further research on the vertex cover P_k problem and its related issues.

Abstract:The continuous improvement of information technology will inevitably promote the arrival of the era of big data.Cloud computing provides a powerful data processing platform for big data.However,data security and privacy issues have aroused great concern.In this paper,we propose a new certificateless public key encryption scheme with multiple keywords search and free of secure channel for big data.We also prove that the proposed scheme can resist chosen keyword attack in random oracle model.The performance analysis shows that,the proposed scheme reduces the computation cost as well as the communication cost compared with the scheme proposed by Peng et al.in 2014.

Abstract:This paper is concerned with the issue of adaptive synchronization for a general class of chaotic memristive competitive neural networks (MCNNs) with mixed time-varying delays and different time scales.By applying Lyapunov functional method and inequality analysis technique,a kind of novel adaptive controllers with feedback control laws are designed to achieve synchronization and exponential synchronization.The synchronization conditions,without need of excessive calculation such as solving linear matrix inequality or computing algebraic conditions,are given,which can be applied in MCNNs with different mathematical models of memristor proposed in the existing literature.Finally,an example with numerical simulations is listed to prove the efficiency and accuracy of the theoretical results.

Abstract:The Vehicular Ad Hoc Network (VANET) enhances the traffic efficiency and improves the traffic environment,however,it brings up security threats such as information tampering,forgery,as well as privacy disclosure.Thus,the message authentication scheme consistent with characteristics of the VANET is in urgent need.In this paper,we take the option of privacy protection scheme for VANET based on vehicle classification in urban transport system,which includes classification and assignment of trust values for different types of vehicles.For private vehicles,a pseudonym multiple signature scheme is employed to sign the message;while for the public vehicles and RSUs without identity privacy protection requirement,we can use the RSA signature scheme to sign messages.At the same time,the signature is required to accumulate the trust value of the strategy to improve the message reliability.Finally,SUMO,MOVE and NS2 are employed to jointly simulate the proposed scheme,and the result shows that the scheme is more flexible and less time-consuming compared with other schemes proposed in references of[19-20].

Abstract:In order to avoid the key escrow problem in identity based cryptosystem and the certificate management problem in traditional public key cryptosystem,we propose a certificateless proxy signature from bilinear pairing.Based on assumption of the computational Diffie-Hellman hardness problem,our scheme is proved secure in random oracle model.Compared with the existing certificateless proxy signature schemes,the proposed scheme has advantage in both computation cost and communication cost.

Abstract:In order to address the security and privacy issues for future e-healthcare systems using lightweight RFID (radio frequency identification) technology,a generalized medical processing model is built,and an improved scheme on existing protocols is thus proposed.In this new scheme,information from the immediate predecessors is fully used to reduce the searching space.Security analysis shows that it can effectively tradeoff the conflicts between the security and scalability,resist all kinds of attacks,support the reuse of RFID tags,and conform to current EPC C1G2 standards.

Abstract:The development of VANETs and cloud computing brings more and more mobile application services for VANETs.Yet vehicles must provide registration information to different cloud servers to obtain their services.In order to achieve efficient authentication in multi-server architecture,this paper proposes an anonymous authentication and key agreement protocol in multi-server architecture for vehicular cloud computing,which realizes a two-way authentication protocol for vehicles and servers,and protects the privacy of the vehicles at the same time.

Abstract:Location based service brings great convenience for people's life.At present,most of the positioning services in indoor environment are based on the wireless network.However,big data makes the user's personal information no longer privacy.In particular,the service provider will obtain the user's personal location information in real timewiththe network-based positioning service.How to protect user's location information is an important issue in the big data era.This paper introduces an offline geomagnetic positioning model for indoor location data privacy protection.This model uses the accelerometer to detect pedestrian gait information and match the magnetic field information detected by the magnetometer with the fingerprint map.It can not only provideindoor location service,but also solve the problem of user's location information disclosure,thus gives an effective solution to user location privacy protection.

Abstract:We propose an access control encryption (ACE) scheme which supports the fully homomorphic operations on the ciphertext,and give a concrete construction from Learning with Error (LWE).Firstly,we show the definition and security model of ACE supporting the fully homomorphic operations under the ciphertext according to the concept of the fully homomorphic encryption (FHE) and ACE.Secondly,we make a black-box construction based on the fully homomorphic encryption which satisfies the certain conditions.Finally,we show a concrete construction based on LWE.

Abstract:In era of big data,how to make full use of data analysis and data mining to effectively detect the spread of infectious diseases is of great significance for epidemic prevention & control as well as for individual security.Voluntary vaccination is an effective way to achieve broad immunity and safety protection for the whole population.Previous research results have showed that an individual's decision on voluntary vaccination is mainly based upon tradeoff between the infection risk and the protective profit,in which the decision of the individual's neighbors in last season is of impact,indicating the influence of strategy-updating for the collective security and protection.This paper studies into the effect of different strategy updates on the voluntary vaccination.The average proportion of vaccination,epidemic scale and total social cost are compared between different strategy updates.Thereafter,a reasonable strategy-updatingisdesigned to achieve relatively big vaccination coverage and small disease outbreak scale with relatively low social cost.

Abstract:Approximate shortest distance query is the basic pattern of graph search.The graph data is usually encrypted in order to protect the security of the outsourced data.The existing encryption schemes use the two-hop labeling model to construct the encryption index,which leads to the high-complexity of index structure and the reduction of query efficiency.This paper proposed an algorithm based on graph compression,which can improve the efficiency of the graph query and support the approximate shortest distance query of encrypted graph.The algorithm uses K-mediods clustering so that the nodes in the graph are divided into K clusters according to the distance.The nodes in each cluster use their central node as agent node.When querying the shortest distance between two points,the point in different clusters uses the proxy node to query distance.The experimental results show that the algorithm can effectively reduce the query time and improve the query efficiency,and the deviation rate of the query result is acceptable.

Abstract:In recent years,large-scale graph analysis has played an important role in big data computing.The classical graph analysis problems include computing the graph diameter,the radius,the girth,the clustering coefficient and various centrality indices.To solve these problems,centralized algorithms generally require square or even cubic time complexity,which is obviously not applicable to large-scale graphs.In this paper,we aim to briefly review some low complexity (linear time) algorithms for these basic graph problems from a perspective of distributed algorithms.In addition,this paper also shows how to prove the lower bound of distributed graph computing by utilizing the communication complexity theory.

Abstract:The context-aware application system is widely used in industrial production and our daily lives.This paper mainly focuses on aspects related to the context-aware application system,such as data collection,secure data transmission & management,and constructs the architecture of the context-aware application system,including the context data acquisition unit,the data transmission network and the cloud data center.The data are collected by sensors,and transmitted to the field supervision unit,then to the cloud data center by the Internet,of which the whole processes are secured through various security protection methods,including sensitive data encryption & isolation,access control,authorization management,audit logs,and backup & recovery.Security of context data is emphasized and practiced in the whole data processes from data collection to data transmission,storage,application,management and so on.

Abstract:Fingerprinting-based localization is one of the most popular indoor localization approaches.In the offline phase,the service provider measures the fingerprint,i.e.,receives signal strength (RSS) samples from various access points (APs) at a number of knownlocations in the target space and stores them in a database.In the online phase,a user sends his location query with his current fingerprint measurement to the server,which will search for the closest fingerprintin the database.Although this approach has been studied for a long time,no existing work considers the privacy requirements for the two sides:the provider wants to protect thecollected fingerprints against the users;while the users want to protect their fingerprint measurements against the service provider to avoid locationleaking.In this paper,we aim to protect the privacy of the users and the service provider at the same time.We propose a privacy-preserving fingerprint matching scheme which uses a cryptographic technique to compute the distance between the fingerprint measured by the user and the fingerprints in the database within the ciphertext space.We show that it well guarantees the privacy requirement of both the two sides in a single localization.To reduce its time overhead,we then present an improved scheme based on the grid division as well as three extensions at the cost of limited privacy loss.To enhance its security,we finally present an effective countermeasure against a special attack leveraging which malicious users could revealfingerprints on the server through repeated localizations.The extensive experiments with a public RSS-fingerprint dataset show that our proposal is fast enough for realtime localization and preserve the localization precision at the same time.

Abstract:For power system components based on nonlinear differential algebraic equations subsystems,a novel algorithm is proposed to study their inverse system control problem.This algorithm does not need complex transformations of controlled output vector and its high order derivative vector,which means better applicability.The procedure of inverse system controller design can be divided into two parts.First,to judge the invertibility of the controlled subsystem using the proposed algorithm.If it is invertible,an α-order integral right inverse system can be constructed by state-feedback and dynamic compensation,with which the decoupling and linearization of the composed systems are achieved.Second,various linear control theories and methods are applied to achieve the desired closed-loop performance.A decentralized nonlinear inverse valve controller is designed for multi-machine power systems based on the proposed method in this paper and the simulation results illustrate its validity.