Anil K. Sarje

A secure dynamic identity based authentication protocol for multi-server architecture

Most of the password based authentication protocols rely on single authentication server for the users authentication. Users verification information stored on the single server is a main point of susceptibility and remains an attractive target for the attacker. In 2009, Hsiang and Shih improved Liao and Wangs dynamic identity based smart card authentication protocol for multi-server environment. However, we found that Hsiang and Shihs protocol is susceptible to replay attack, impersonation attack and stolen smart card attack. Moreover, the password change phase of Hsiang and Shihs protocol is incorrect. This paper presents a secure dynamic identity based authentication protocol for multi-server architecture using smart cards that resolves the aforementioned security flaws, while keeping the merits of Hsiang and Shihs protocol. It uses two-server paradigm in which different levels of trust are assigned to the servers and the users verifier information is distributed between these two servers known as the service provider server and the control server. The service provider server is more exposed to the clients than the control server. The back-end control server is not directly accessible to the clients and thus it is less likely to be attacked. The users smart card uses stored information in it and random nonce value to generate dynamic identity. The proposed protocol is practical and computationally efficient because only nonce, one-way hash functions and XOR operations are used in its implementation. It provides a secure method to change the users password without the servers help. In e-commerce, the number of servers providing the services to the user is usually more than one and hence secure authentication protocols for multi-server environment are required.

An improvement of Xu et al.'s authentication scheme using smart cards

In 2009, Xu et al. found that Lee et al.s [3] scheme is vulnerable to offline password guessing attack. Xu et al. also demonstrated that Lee and Chius [4] scheme is vulnerable to forgery attack. Furthermore, Lee and Chius scheme does not achieve mutual authentication and thus can not resist malicious server attack. Therefore, Xu et al. proposed an improved scheme that inherits the merits of Lee et al.s and Lee and Chius schemes and resists different possible attacks. However, we found that Xu et al.s scheme is vulnerable to forgery attack. This paper presents an improved scheme to resolve the aforementioned problem, while keeping the merits of Xu et al.s scheme.

Distributed real time database systems: background and literature review

Today’s real-time systems (RTS) are characterized by managing large volumes of dispersed data making real-time distributed data processing a reality. Large business houses need to do distributed processing for many reasons, and they often must do it in order to stay competitive. So, efficient database management algorithms and protocols for accessing and manipulating data are required to satisfy timing constraints of supported applications. Therefore, new research in distributed real-time database systems (DRTDBS) is needed to investigate possible ways of applying database systems technology to real-time systems. This paper first discusses the performance issues that are important to DRTDBS, and then surveys the research that has been done so far on the issues like priority assignment policy, commit protocols and optimizing the use of memory in non-replicated/replicated environment pertaining to distributed real time transaction processing. In fact, this study provides a foundation for addressing performance issues important for the management of very large real time data and pointer to other publications in journals and conference proceedings for further investigation of unanswered research questions.

An Efficient Gateway Discovery in Ad Hoc Networks for Internet Connectivity

Integration of MANET with the Internet is a challenging problem. It is important that dynamically deployed wireless ad hoc networks should also gain access to Internet multimedia contents through these fixed networks. When a mobile node in an Ad Hoc network wants to communicate with a node on the Internet, it has to find an efficient and reliable Internet gateway. For this purpose, the node either can send solicitation message or may depend on periodic gateway advertisement. Gateway discovery time has strong influence on packet delay and throughput. In most of the cases, a mobile node uses a number of physical hops to a gateway to communicate with a fixed host connected to an Internet. However, a minimum hop path may not always be efficient if some nodes along the path have longer queue of waiting packets. The focus of this paper is on devising an efficient proactive gateway discovery algorithm that takes into account the size of interface queue in addition to the traditional minimum hop metric to select an efficient gateway. In the MANET domain, AODV routing protocol has been used. This approach also allows an efficient handoff from one gateway to another gateway and still maintains a seamless connectivity to a fixed host. In this paper, impacts of this new metric on the gateway discovery performance are investigated. Simulation results indicate that our protocol outperforms other approaches.

Comparative performance analysis of LANMAR, LAR1, DYMO and ZRP routing protocols in MANET using Random Waypoint Mobility Model

In this paper, we compare performance of some routing protocols for Mobile Ad-Hoc Networks (MANETs). A Mobile Ad-Hoc Network (MANET) is a collection of wireless mobile nodes that communicates with each other without using any existing infrastructure or centralized administration. In MANET, due to mobility of nodes network topology changes frequently and thus, routing becomes a challenging task. A variety of routing protocols with varying network conditions are analyzed to find an optimized route from a source to some destination. This paper presents performance comparison of four popular mobile ad-hoc network routing protocols i.e. Landmark Ad-hoc Routing Protocol (LANMAR), Location Aided Routing scheme 1 (LAR1), Dynamic MANET On-Demand (DYMO) and Zone Routing Protocol (ZRP) in variable pause time. We used well known network simulator QualNet 5.0 from scalable networks to evaluate the performance of these protocols. The performance analysis is based on different network metrics such as average jitter, packet delivery ratio, average end-to-end delay and throughput.

A weighted cache replacement policy for location dependent data in mobile environments

Developing widely useful mobile computing applications presents difficult challenges. On one hand, mobile users demand intuitive user interfaces, fast response times, and deep relevant content. On the other hand, mobile devices have limited processing, storage, power, display, and communication resources. Caching frequently accessed data items on the mobile client is an effective technique to improve the system performance in mobile environment. Due to cache size limitation, the choice of cache replacement technique to find a suitable subset of items for eviction from cache becomes important. In this paper, we propose a new cache replacement policy for location dependent data in mobile environment. The proposed policy selects the predicted region based on clients movement and uses it to calculate the weighted data distance of an item. This makes the policy adaptive to clients movement pattern and provides importance to the regions around clients position. This is unlike earlier policies that consider the directional/non-directional data distance only. We call our policy the Weighted Predicted Region based Cache Replacement Policy (WPRRP). Simulation results show that the proposed policy significantly improves the system performance in comparison to previous schemes in terms of cache hit ratio.

A Routing Protocol for Delay-Sensitive Applications in Mobile Ad Hoc Networks

The Ad hoc On Demand Distance Vector (AODV) routing protocol is intended for use by mobile nodes in ad hoc networks. To provide quality of service, extensions can be added to the messages used during route discovery. These extensions specifythe service requirements which must be met by nodes rebroadcasting a route request (RREQ) or returning a route reply (RREP) for a destination. In order to provide quality delivery to delay sensitive applications such as voice and video, it is extremely important that mobile ad hoc networks provide quality of service (QoS) support in terms of bandwidth and delay. In spite of using IEEE 802.11 as medium access control (MAC), most of the ad hoc routing protocols do not consider contention time which occurs in the medium reservation. Large contention times can be more critical than hop counts in determining the end-to-end delay. Most existing routing protocols for mobile ad hoc networks are designed to search for the shortest path with minimum hop counts. However, the shortest routes do not always provide the best performance, especially when there are congested nodes along these routes. In this paper we propose an on demand delay based quality of service (QoS) routing protocol (AODV-D) to ensure that delay does not exceed a maximum value for mobile ad hoc networks. This protocol will take into consideration MAC layer channel contention information and the number of packets in the interface queue in addition to minimum hops.

SWIFT--A new real time commit protocol

Although there are several factors contributing to the difficulty in meeting distributed real time transaction deadlines, data conflicts among transactions, especially in commitment phase, are the prime factor resulting in system performance degradation. Therefore, design of an efficient commit protocol is of great significance for distributed real time database systems (DRTDBS). Most of the existing commit protocols try to improve system performance by allowing a committing cohort to lend its data to an executing cohort, thus reducing data inaccessibility. These protocols block the borrower when it tries to send WORKDONE/PREPARED message [1, 6, 8, 9], thus increasing the transactions commit time. This paper first analyzes all kind of dependencies that may arise due to data access conflicts among executing-committing transactions when a committing cohort is allowed to lend its data to an executing cohort. It then proposes a static two-phase locking and high priority based, write-update type, ideal for fast and timeliness commit protocol i.e. SWIFT. In SWIFT, the execution phase of a cohort is divided into two parts, locking phase and processing phase and then, in place of WORKDONE message, WORKSTARTED message is sent just before the start of processing phase of the cohort. Further, the borrower is allowed to send WORKSTARTED message, if it is only commit dependent on other cohorts instead of being blocked as opposed to [1, 6, 8, 9]. This reduces the time needed for commit processing and is free from cascaded aborts. To ensure non-violation of ACID properties, checking of completion of processing and the removal of dependency of cohort are required before sending the YES-VOTE message. Simulation results show that SWIFT improves the system performance in comparison to earlier protocol. The performance of SWIFT is also analyzed for partial read-only optimization, which minimizes intersite message traffic, execute-commit conflicts and log writes consequently resulting in a better response time. The impact of permitting the cohorts of the same transaction to communicate with each other [5] on SWIFT has also been analyzed.

VM provisioning policies to improve the profit of cloud infrastructure service providers

Cloud computing is an emerging technology in the IT world. Some features of cloud, such as low cost, scalability, robustness and availability are attracting large-scale industries as well as small business towards cloud. A virtual machine (VM) can be defined as a software that can run its own operating systems and applications like an operating system in physical computer. As the number of users increases, allocation of resources and scheduling become a complex task. The optimization of VM provisioning policies offer improvement like increasing providers profit, energy savings and load balancing in large data centres. In cloud computing when resource requirement of users requests exceed resources limits of cloud provider, to fulfil the requests the cloud provider outsources to other cloud providers resources, this concept is known as cloud federation. In this paper we propose an algorithm for VM provisioning in federated cloud environment. The approach tries to improve the cloud providers profit. We have used the CloudSim to find-out the results and result show that how Cloud federation help to Cloud providers in order to improve its profit.

A QoS routing protocol for delay-sensitive applications in mobile ad hoc networks

The Ad hoc On Demand Distance Vector (AODV) routing protocol is intended for use by mobile nodes in ad hoc networks. To provide quality of service, extensions can be added to the messages used during route discovery. These extensions specify the service requirements which must be met by nodes rebroadcasting a route request (RREQ) or returning a route reply (RREP) for a destination. In order to provide quality delivery to delay sensitive applications such as voice and video, it is extremely important that mobile ad hoc networks provide quality of service (QoS) support in terms of bandwidth and delay. Most existing routing protocols for mobile ad hoc networks are designed to search for the shortest path with minimum hop count. However, the shortest routes do not always provide the best performance, especially when there are congested nodes along these routes. In this paper we propose an on demand delay based quality of service (QoS) routing protocol (AODV-D) to ensure that delay does not exceed a maximum value for mobile ad hoc networks. This protocol will take into consideration MAC layer channel contention information and number of packets in the interface queue in addition to minimum hops. The protocol is implemented and simulated using GlomoSim simulator. Performance comparisons of the proposed AODV-D protocol against AODV, and QS-AODV is presented and shown that the proposed algorithm performs well.