A Secure Session Key Distribution Scheme for Group Communications

In a secure group communication system, messages must be encrypted before being transmitted to group members to prevent unauthorized access. In many secure group communication schemes, whenever a member leaves or joins the group, group center (GC) immediately changes the common encryption key and sends the new key to all valid members for forward and backward secrecy. If valid members are not on-line, they will miss the re-keying messages and will not be able to decrypt any ciphertext. Therefore, group members must be able to store the state of the system. In some applications, like global positioning systems (GPS) or pay-per-view systems, it is not reasonable to ask group members to stay on-line all the time and save the changes to the system. A hierarchical binary tree-based key management scheme are proposed for a secure group communication. This scheme reduces the key storage requirement of GC to a constant size and the group members are not required to be on-line constantly (stateless).

SECURE GROUP COMMUNICATIONS FOR LARGE DYNAMIC MULTICAST GROUP

As the major problem in multicast security, the group key management has been the focus of research But few results are satisfactory. In this paper, the problems of group key management and access control for large dynamic multicast group have been researched and a solution based on SubGroup Secure Controllers (SGSCs) is presented, which solves many problems in IOLUS system and WGL scheme.

A new group key management scheme based on keys tree, XOR operation and one-way function

By introducing XOR operation and one-way function chains to group key management schemes based on the keys tree, a new group key management scheme based on the keys tree, XOR operation and one-way function chains is proposed. Initialization, member adding and member evicting operations are introduced. The new scheme is compared with three other group key management schemes which are based on the keys tree： SKDC, LKH, and OFF. As far as transmission, computation and storage costs are concerned, the performance of the new group key management scheme is the best. The security problem of the new scheme is analyzed. This new scheme provides backward and forward security, i.e.. newly admitted group members cannot read previous multicast messages and evicted members cannot read future multicast messages, even with collusion by many arbitrarily evicted members.

Decision Tree Based Key Management for Secure Group Communication

Group communication is widely used by most of the emerging network applications like telecommunication,video conferencing,simulation applications,distributed and other interactive systems.Secured group communication plays a vital role in case of providing the integrity,authenticity,confidentiality,and availability of the message delivered among the group members with respect to communicate securely between the inter group or else within the group.In secure group communications,the time cost associated with the key updating in the proceedings of the member join and departure is an important aspect of the quality of service,particularly in the large groups with highly active membership.Hence,the paper is aimed to achieve better cost and time efficiency through an improved DC multicast routing protocol which is used to expose the path between the nodes participating in the group communication.During this process,each node constructs an adaptive Ptolemy decision tree for the purpose of generating the contributory key.Each of the node is comprised of three keys which will be exchanged between the nodes for considering the group key for the purpose of secure and cost-efficient group communication.The rekeying process is performed when a member leaves or adds into the group.The performance metrics of novel approach is measured depending on the important factors such as computational and communicational cost,rekeying process and formation of the group.It is concluded from the study that the technique has reduced the computational and communicational cost of the secure group communication when compared to the other existing methods.

Overlay Share Mesh for Interactive Group Communication with High Dynamic

An overlay share mesh infrastructure is presented for high dynamic group communication systems, such as distributed interactive simulation (DIS) and distributed virtual environments (DVE). Overlay share mesh infrastructure can own better adapting ability for high dynamic group than tradition multi-tree multicast infrastructure by sharing links among different groups. The mechanism of overlay share mesh based on area of interest (AOI) was discussed in detail in this paper. A large number of simulation experiments were done and the performance of mesh infrastructure was studied. Experiments results proved that overlay mesh infrastructure owns better adaptability than traditional multi-tree infrastructure for high dynamic group communication systems.

HUFFMAN-BASED GROUP KEY ESTABLISHMENT SCHEME WITH LOCATION-AWARE

Time efficiency of key establishment and update is one of the major problems contributory key managements strive to address.To achieve better time efficiency in key establishment,we propose a Location-based Huffman(L-Huffman) scheme.First,users are separated into several small groups to minimize communication cost when they are distributed over large networks.Second,both user's computation difference and message transmission delay are taken into consideration when Huffman coding is employed to forming the optimal key tree.Third,the combined weights in Huffman tree are located in a higher place of the key tree to reduce the variance of the average key generation time and minimize the longest key generation time.Simulations demonstrate that L-Huffman has much better performance in wide area networks and is a little better in local area network than Huffman scheme.

Integrating IPsec within OpenFlow Architecture for Secure Group Communication

Network security protocols such as IPsec have been used for many years to ensure robust end-to-end communication and are important in the context of SDN. Despite the widespread installation of IPsec to date, per-packet protection offered by the protocol is not very compatible with OpenFlow and tlow-like behavior. OpenFlow architecture cannot aggregate IPsee-ESP flows in transport mode or tunnel mode because layer-3 information is encrypted and therefore unreadable. In this paper, we propose using the Security Parameter Index （SPI） of IPsec within the OpenFlow architecture to identify and direct IPsec flows. This enables IPsec to conform to the packet-based behavior of OpenFlow architecture. In addition, by distinguishing between IPsec flows, the architecture is particularly suited to secure group communication.

Algorithm for Delay-Constrained Minimal Cost Group Multicasting

Group multicast routing algorithms satisfying quality of service requirements of real-time applications are essential for high-speed networks. A heuristic algorithm was presented for group multicast routing with bandwidth and delay constrained. A new metric was designed as a function of available bandwidth and delay of link. And source-specific routing trees for each member were generated in the algorithm by using the metric, which satisfy member′s bandwidth and end-to-end delay requirements. Simulations over random network were carried out to compare the performance of the proposed algorithm with that from literature.Experimental results show that the algorithm performs better in terms of network cost and ability in constructing feasible multicast trees for group members. Moreover,the algorithm can avoid link blocking and enhance the network behavior efficiently.

Applying Communicative Teaching Method in English-teaching Classroom

Communicative language teaching is generally accepted in the field of second language teaching. In this paper, the author introduces a model of communicative language teaching. The authors also mention some practical requirements and methods in the application of this model, such as authentic materials and group work.

Towards Interaction,Communication and Integration of Ethnic Groups with Commonality:A Comparison of Inner Mongolia,Guangxi and Ningxia Autonomous Region

One crucial measure of strengthening and advancing the Party's work on ethnic affairs in the new era is to promote interaction,communication and integration of various ethnic groups,so as to enhance commonality.Entering the new era,Inner Mongolia,Guangxi and Ningxia have achieved remarkable results in encouraging interaction,communication and integration of various ethnic groups.By comparatively analyzing successes of the three autonomous regions through the perspective of promoting commonality,this article summarizes the following strategic revelations:1)we should comprehensively implement the Party's ethnic policies and ensure theactual implementation of mutual interaction,mutual communication and mutual integration of ethnic groups;2)we should proactively promote the substantial progress of the economy,so as to provide solid material foundation for mutual interaction,mutual communication and mutual integration of ethnic groups;3)we should facilitate activities that promote ethnic unity and progress,so that the promotion of interaction,communication and mutual integration of ethnic groups can be seen,be felt and gain actual outcomes;4)we should take measures that suit to local conditions and explore all-round embedding mechanisms in order to foster the ethos for mutual interaction,mutual communication and mutual integration of ethnic groups;5)we should make every effort to forge a strong sense of community for the Chinese nation and orient precisely to the cause of encouraging mutual interaction,mutual communication and mutual integration of ethnic groups.

Fault Tolerance and Recovery for Group Communication Services in Distributed Networks

Group communication services （GCSs） are becoming increasingly important as a wide field of promising applications has emerged to serve millions of users distributed across the world.However,it is challenging to make the service fault tolerance and scalable to fulfill the voluminous demand of users in a distributed network （DN）.While many reliable group communication protocols have been dedicated to addressing such a challenge so as to accommodate the changes in the network,they are often costly or require complicated strategies to handle the service interruptions caused by node departures or link failures,which hinders the service practicability.In this paper,we present two schemes to address the challenges.The first one is a location-aware replication scheme called NS,which makes replicas in a dispersed fashion that enables the services on nodes to gain immunity of failures with different patterns （e.g.,network partition and single point failure） while keeping replication overhead low.The second one is a novel failure recovery scheme that exploits the independence between service recovery and structure recovery in time domain to achieve quick failure recovery.Our simulation results indicate that the two proposed schemes outperform the existing schemes and simple alternative schemes in service success rate,recovery latency,and communication cost.

Prediction of Group Delay Distribution Around Receiving Point Using Modified IRI Model and IGRF Model

The international reference ionosphere （IRI） model is generally accepted standard ionosphere model. It describes the ionosphere environment in quiet state and predicts the ionosphere parameters within a certain precision. In this paper, we have made a breakthrough in the application of the IRI model by modifying the model for regions of China. The main objectives of this modification are to construct the ionosphere parameters foF2 and M （3000） F2 by using the Chinese reference ionosphere （CRI） coefficients, appropriately increase hmE and hmF2 height, reduce the thickness of F layer, validate the parameter by the measured values, and solve the electron concentration distribution with quasi-parabolic segment （QPS）. In this paper, 3D ray tracing algorithm is constructed based on the modified IRI model and international geomagnetic reference field （IGRF） model. In short-wave propagation, it can be used to predict the electromagnetic parameters of the receiving point, such as the receiving area, maximum useable frequency （MUF） and the distribution of the group delay etc., which can help to determine the suitability of the communication. As an example, we estimate the group delay distributions around Changchun in the detection from Qingdao to Changchun using the modified IRI model and IGRF model, and provide technical support for the short-wave communication between the two cities.

Lightweight Trusted Security for Emergency Communication Networks of Small Groups

Public communication infrastructures are susceptible to disasters. Thus, the Emergency Communication Networks(ECNs) of small groups are necessary to maintain real-time communication during disasters. Given that ECNs are self-built by users, the unavailability of infrastructures and the openness of wireless channels render them insecure. ECN security, however, is a rarely studied issue despite of its importance. Here, we propose a security scheme for the ECNs of small groups. Our scheme is based on the optimized Byzantine Generals’ Problem combined with the analysis of trusted security problems in ECNs. Applying the Byzantine Generals’ Problem to ECNs is a novel approach to realize two new functions, debugging and error correction, for ensuring system consistency and accuracy. Given the limitation of terminal devices, the lightweight fast ECDSA algorithm is introduced to guarantee the integrity and security of communication and the efficiency of the network. We implement a simulation to verify the feasibility of the algorithm after theoretical optimization.

SeaHttp:A Resource-Oriented Protocol to Extend REST Style for Web of Things

Web of Things （WoT） makes it possible to connect tremendous embedded devices to web in Representational State Transfer （REST） style. Some lightweight RESTful protocols have been proposed for the WoT to replace the HTTP protocol running on embedded devices. However, they keep the principal characteristic of the REST style. In particular, they support one-to-one requests in the client-server mode by four standard RESTful methods （GET, PUT, POST, and DELETE）. This characteristic is however inconsistent with the practical networks of embedded devices, which typically perform a group operation. In order to meet the requirement of group communication in the WoT, we propose a resource-oriented protocol called SeaHttp to extend the REST style by introducing two new methods, namely BRANCH and COMBINE respectively. SeaHttp supports parallel processing of group requests by means of splitting and merging them. In addition SeaHttp adds spatiotemporal attributes to the standard URI for naming a dynamic request group of physical resource. Experimental results show that SeaHttp can reduce average energy consumption of group communication in the WoT by 18.5%, compared with the Constrained Application Protocol （CoAP）.

Parallelization Load Balance Strategy for a Global Grid-Point Model

The Global/Regional Assimilation and PrEdiction System（GRAPES）is a new-generation operational numerical weather prediction（NWP）model developed by the China Meteorological Administration（CMA）.It is a grid-point model with a code structure different from that of spectral models used in other operational NWP centers such as the European Centre for Medium-Range Weather Forecasts（ECMWF）,National Centers for Environmental Prediction（NCEP）,and Japan Meteorological Agency（JMA）,especially in the context of parallel computing.In the GRAPES global model,a semi-implicit semi-Lagrangian scheme is used for the discretization over a sphere,which requires careful planning for the busy communications between the arrays of processors,because the Lagrangian differential scheme results in shortened trajectories interpolated between the grid points at the poles and in the associated adjacent areas.This means that the latitude-longitude partitioning is more complex for the polar processors.Therefore,a parallel strategy with efficient computation,balanced load,and synchronous communication shall be developed.In this paper,a message passing approach based on MPI（Message Passing Interface）group communication is proposed.Its key-point is to group the polar processors in row with matrix-topology during the processor partitioning.A load balance task distribution algorithm is also discussed.Test runs on the IBM-cluster 1600 at CMA show that the new algorithm is of desired scalability,and the readjusted load balance scheme can reduce the absolute wall clock time by 10% or more.The quasi-operational runs of the model demonstrate that the wall clock time secured by the strategy meets the real-time needs of NWP operations.

A three-level authenticated conference key establishment protocol for UMTS networks

A conference key establishment protocol allows a group of conferees to agree on a secret key shared among them for secure group communication.This paper proposes a three-level conference key establishment protocol based on the Universal Mobile Telecommunications System (UMTS) framework to establish a group-level key,home location register (HLR) level keys,and visitor location register (VLR) level keys simultaneously for a group of conferees.The group-level key is used to secure the communications for all conferees,the HLR-level key is for those within the same HLR domain,and the VLR-level key is for those within the same VLR domain.The group-level key can be used for securing inter-domain group-oriented applications such as commercial remote conferencing systems.The HLRand VLR-level keys can be used for securing intra-domain subgroup applications (e.g.,location-based or context-aware services) and dynamic key updating.Since our proposed protocol exploits existing UMTS security functions and the exclusive-or operation,it is compatible with UMTS architecture.This means that it is fast and easy to implement on the existing UMTS architecture.Furthermore,the proposed protocol has low computational complexities and can provide cost effectiveness,load-amortization,scalability,user authentication,key establishment,key confirmation,key updating,and lawful interception.