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CHAPTER 2

LITERATURE SURVEY

2.1 WIRELESS MESH NETWORKS

Various wireless networks evolve into the next generation to provide

better services. A key technology, wireless mesh networks (WMNs) has emerged

recently. WMNs have many advantages such as low up-front cost, easy network

maintenance, robustness, and reliable service coverage. Wireless Mesh Networks

(WMNs) consist of mesh routers and mesh clients, where mesh routers have

minimal mobility and form the backbone of WMNs. Each node operates not only as

a host but also as a router, forwarding packets on behalf of other nodes that may not

be within direct wireless transmission range of their destinations. A WMN is

dynamically self-organized and self-configured, with the nodes in the network

automatically establishing and maintaining mesh connectivity among themselves

and conventional clients.

The integration of WMNs with other networks such as the Internet,

cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, etc., can be

accomplished through the gateway and bridging functions in the mesh routers. Mesh

clients can be either stationary or mobile, and can form a client mesh network

among themselves and with mesh routers. WMNs are anticipated to resolve the

limitations and to significantly improve the performance of wireless networks,

Wireless Local Area Networks (WLANs), Wireless Personal Area Networks

(WPANs), and Wireless Metropolitan Area Networks (WMANs). They are

undergoing rapid progress and inspiring numerous deployments. WMNs will deliver

wireless services for a large variety of applications in personal, local, campus, and

metropolitan areas. Despite recent advances in wireless mesh networking, many

research challenges remain in all protocol layers. The authors [1] present a detailed

study and open research issues in WMNs. System architectures and applications of

WMNs are described, followed by discussing the critical factors influencing

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protocol design. Theoretical network capacity and the state-of-the-art protocols for

WMNs are explored with an objective to point out a number of open research issues.

Finally, test-beds, industrial practice, and current standard activities related to

WMNs are highlighted.

The authors [2] summarize the technologies and challenges related to

wireless mesh networks. Using technologies like 802.11i, WPA in wireless LAN,

enterprise deployments have finally begun to embrace wireless access networks.

Wireless LAN technology has often been approached cautiously in enterprise

deployments, partly due to well-known and easily exploitable attacks on early

802.11 security technology and partly due to the lack of physical control of the

access medium. Over the past several years, early adoption of some 802.11i security

features by the Wi-Fi Alliance in the Wi-Fi Protected Access (WPA) interoperability

forums, as well as the standardization of the 802.11i security amendment, have

greatly improved the authentication, encryption and integrity security capabilities.

However, new challenges with wireless mesh architectures using 802.11, the

pending solutions with 802.11s, and the security pitfalls of metro Wi-Fi networks

rekindle many of the original threats and technology maturity issues with ubiquitous

wireless access networking. The security technologies will cover current industry

capabilities and 802.11s, and the overall security architecture.

Unlike traditional wireless networks [3], in Hybrid Wireless Mesh

Network (HWMN), hosts may rely on each other to keep the network connected.

Operators and wireless internet service providers are choosing HWMNs to offer

Internet connectivity, as it allows fast, easy and affordable network deployments.

One main challenge in design of these networks is their vulnerability to security

attacks. The authors investigate the main security issues focusing on the most

vulnerable part of the hybrid WLAN mesh infrastructure which concerns the ad hoc

network part. Through the proposed architecture, security architecture for operator’s

hybrid WLAN Mesh Network, author identifies the new challenges and

opportunities posed by this emerging networking environment and explore

approaches to secure users, data and communications. By analyzing the strengths

and weaknesses of secured routing protocols, designed a new robust routing

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structure called Macrograph (MG). MG structure is extracted from the mesh ad hoc

network for each communication to be established between a source and a

destination. Especially, MG is a robust structure based on node-disjoint path routing

scheme and dynamic trust management that can be adapted to respond to

applications’ security requirements.

The Authors [4] has given some recommendations for wireless mesh

backhaul designs and implementations. Radio links are used to provide backhaul

connectivity for base stations of mobile networks, in cases in which cable-based

alternatives are not available and cannot be deployed in an economic or timely

manner. While such wireless backhauls have been predominantly used in redundant

tree and ring topologies in the past, mobile network operators have become

increasingly interested in meshed topologies for carrier-grade wireless backhauls.

However, wireless mesh backhauls are potentially more susceptible to security

vulnerabilities, given that radio links are more exposed to tampering and given their

higher system complexity. This article extends prior security threat analysis of 3rd

generation mobile network architectures for the case of wireless mesh backhauls. It

presents a description of the security model for the considered architecture and

provides a list of the basic assumptions, security objectives, assets to be protected

and actors of the analysis. On this foundation, potential security threats are analyzed,

discussed and then assessed for their corresponding risk. The result of this risk

assessment is then used to define a set of security requirements.

2.2 WIRELESS MESH NETWORKS SECURITY

It is challenging to design a key management scheme in current mission-

critical networks to fulfill the required attributes of secure communications, such as

data integrity, authentication, confidentiality, non-repudiation and service

availability. Mission-critical networks show great potential in emergency response

and/or recovery, health care, critical infrastructure monitoring, etc. Such mission-

critical applications demand security service as “anywhere”, “anytime” and

“anyhow” [5]. The authors present a self-contained public key management scheme,

called SMOCK, which achieves almost zero communication overhead for

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authentication, and offers high service availability. In this scheme, small numbers of

cryptographic keys are stored off-line at individual nodes before they are deployed

in the network. To provide good scalability in terms of number of nodes and storage

space, authors utilize a combinatorial design of public-private key pairs, which

means nodes combine more than one key pair to encrypt and decrypt messages. The

cryptographic key management is challenging due to the following characteristics of

wireless communications:

� Unreliable Communications and Limited Bandwidth

� Network Dynamics

� Large Scale

� Resource Constraints

Using Wireless Mesh Networks (WMNs) to offer internet connectivity is

becoming a popular choice for Wireless Internet Service Providers as it allows a

fast, easy and inexpensive network deployment [6]. However, security in WMNs is

still in its infancy as very little attention has been devoted so far to this topic by the

research community.

Wireless Mesh Networks (WMNs) represent a good solution to providing

wireless Internet connectivity in a sizable geographic area; this new and promising

paradigm allows for network deployment at a much lower cost than with classic

Wi-Fi networks. A large number of Wireless Hot Spots (WHSs) is needed to deploy

a Wi-Fi network; extending further the network coverage requires the deployment of

additional WHSs, which is costly and delicate. In WMNs, it is possible to cover the

same area (or even a larger one) with only one WHS and several wireless Transit

Access Points (TAPs). The TAPs are not connected to the wired infrastructure and

therefore rely on the WHS to relay their traffic. The cost of a TAP is much lower

than that of the WHS, which makes the use of WMNs a compelling economical

case; WMNs are thus suitable for areas where it is costly to install a traditional Wi-

Fi network (e.g., buildings that do not have existing data cabling for WHSs) or for

the deployment of a temporary wireless network.

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In cellular networks, a given area is divided into cells and each cell is

under the control of a base station. Each base station handles a certain number of

mobile clients that are in its immediate vicinity (i.e., communication between the

mobile clients and the base station is single-hop) and it plays an important role in the

functioning of the cellular network; the entity that plays an equivalent role in WMNs

would be the WHS. WMNs represent a simple and inexpensive solution to extend

the coverage of a WHS. However, the deployment of such networks is slowed down

by the lack of security guarantees. Author has analyzed the characteristics of WMNs

and has deduced three fundamental network operations that need to be secured: (i)

the detection of corrupt TAPs, (ii) the definition and use of a secure routing

protocol, and (iii) the definition and enforcement of a proper fairness metric in

WMNs. The author has proposed some solutions to secure these operations. Finally,

the author has described two future WMNs (vehicular networks and multi-operator

WMNs) and has briefly analyzed the new security challenges they introduce.

The architecture of the WMN is a connectionless-oriented, mobile and

dynamic traffic of routed packets [7]. The mesh infrastructure environment easily

forms multiple chains of wireless LANs (WLAN) coupled with the simultaneous

multi hop transmission of data packets from peripherals via mobile gateways to the

wireless cloud. WMN operates as an access network to other communication

technologies. This exposes the WMN to numerous security challenges not only in

the mesh transmission operation security but also in the overall security against

foreign attacks. The authors survey and identify the security vulnerabilities in

Internet Protocol (IP) broadband networks, the security challenges in the routing

layer of the WMN and explore new concepts to solving security challenges in WMN

using Traffic Engineering (TE) security resolution mechanisms.

In the paper author explores the security threats in WMN over a

broadband network. Determination and investigation of the security solution using

traffic engineering mechanism were explored. Author has tested the influence of

security mechanisms over increased traffic loads and hop-count. For multi-layer

comparative analysis with the traditional 802.11i, author has conducted a test for the

observation of the influence of node mobility in a multihop scenario. Further

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evaluation was done on the network load influence, end-to-end traffic delays and

delivery ratio in attack simulated scenarios. Observations of the technical

advantages using a derived and adapted technique in traffic engineering are carried

out. The proposed VPN-IPSec solution applied to the WMN security shows

enhanced overall performance.

Severe security threats such as DDoS also comparatively more effective

security resolution in WMN. The proposed management model security technique

demonstrates that a distributed security failure caused by traffic flooding, grey hole

and black hole DDoS in WMN security can be prevented and resolved using VPN-

IPSec. The security model shows efficient performance in intrusion detection and

prevention mechanism too. Analysis of the investigation shows high performance in

the different metrics used. In the analysis, author notices that it will be very hard to

provide an effective security for multi-hopped wireless mesh network because of its

inherent architectural weakness. However, author proposes a mutual combination

and use of cooperative IP communication security mechanisms in the prevention and

defense of security threats and attacks in the WMN as shown by the IPSec and

MPLS-VPN technique. The VPN-IPSec through authentication, encryption,

cryptography and tunneling and IP security configuration and operational

mechanisms of the MPLS-TE lowers the overhead and processing of the WMN. The

improved VPN-IPSec integrates most of the security measures needed to

comprehensively secure both the data traffic and the infrastructure wireless mesh

network. The authors analyze the advantages, comparative strengths and weakness

in the use of traffic engineering based on simulation results and evaluations.

Wireless mesh networks (WMNs) have emerged recently as a technology

for next-generation wireless networking [8]. The authors propose MobiSEC, a

complete security architecture that provides both access control for mesh users and

routers as well as security and data confidentiality of all communications that occur

in the WMN. MobiSEC extends the IEEE 802.11i standard exploiting the routing

capabilities of mesh routers; after connecting to the access network as generic

wireless clients, new mesh routers authenticate to a central server and obtain a

temporary key that is used both to prove their credentials to neighbor nodes and to

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encrypt all the traffic transmitted on the wireless backbone links. A key feature in

the design of MobiSEC is its independence from the underlying wireless technology

used by network nodes to form the backbone; furthermore, MobiSEC permits

seamless mobility of both mesh clients and routers. Have Implemented MobiSEC in

a real-life test-bed and measured its performance in different network scenarios.

Numerical results show that the proposed architecture increases considerably the

WMN security with a negligible impact on the network performance, thus

representing an effective solution for wireless mesh networking.

MobiSEC tackles the security problems of both the access and backbone

areas of WMNs, providing an effective and transparent security solution for end

users and mesh nodes. Author implements the proposed security architecture in

Mobi- MESH, a complete wireless mesh network framework, and has tested it in

several realistic network scenarios.

A simple self-propagating worm can quickly spread across the Internet

and cause severe damage to the society [9]. Facing this great security threat, need to

build an early detection system that can detect the presence of a worm in the Internet

as quickly as possible in order to give people accurate early warning information

and possible reaction time for counteractions. This paper presents an Internet worm

monitoring system. Then, based on the idea of “detecting the trend, not the burst” of

monitored illegitimate traffic, author present a “trend detection” methodology to

detect a worm at its early propagation stage by using Kalman �lter estimation, which

is robust to background noise in the monitored data. In addition, for uniform-scan

worms such as Code Red, can effectively predict the overall vulnerable population

size, and estimate accurately how many computers are really infected in the global

Internet based on the biased monitored data. For monitoring a non uniform scan

worm, especially a sequential-scan worm such as Blaster, author show that it is

crucial for the address and space covered by the worm monitoring system to be as

distributed as possible.

Author proposes a monitoring and early detection system for Internet

worms to provide an accurate triggering signal for mitigation mechanisms in the

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early stage of a future worm. Such a system is needed in view of the propagation

scale and the speed of the past worms. It has been lucky that the previous worms

have not been very malicious; the same cannot be said for the future worms. The

analysis and simulation studies indicate that such a system is feasible, and the “trend

detection” methodology poses many interesting research issues. This paper will

generate interest and participation in this topic, and eventually lead to an effective

Internet worm monitoring and early detection system.

Since the days of the Morris worm, the spread of malicious code has been

the most imminent menace to the Internet. Worms use various scanning methods to

spread rapidly [10]. Worms that select scan destinations carefully can cause more

damage than worms employing random scan. This paper analyzes various scan

techniques. Author proposes a generic worm detection architecture that monitors

malicious activities and evaluates an algorithm to detect the spread of worms using

real time traces and simulations. The author finds that the solution can detect worm

activities even when only 4% of the vulnerable machines are infected. The results

bring insight to the future battle against worm attacks.

When the attackers are more sophisticated, probing is fundamentally not a

costly process. From the discussions above, it seems that the game would favor the

attackers when the Internet links are fast enough and the size of the code is not

critical to the propagation speed. This does not imply that monitoring is of no use. In

future, an efficient traffic monitoring infrastructure will be an important part of the

global intrusion detection systems. A consequence of the worm detection method is

that the attackers will have to use a limited number of IP addresses to scan the

Internet. Therefore, the impact of worm scanning on the Internet traffic will be

reduced.

The author finds that as the backbone link speeds and hosts of greater

capacity are affordable to the attackers, it will be more difficult for us to detect

worm scanning from the Internet traffic. However, the detection methods can still be

useful in that it forces the attacker to use lesser traffic and scan more slowly and

cautiously. Author has designed two new scan techniques, Routable scan and

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Divide-Conquer scan. Basically, they both use the idea of a routable IP address list

as the destination base where the scan object is selected. A routable worm is easy to

implement; it poses a big menace to the network security. Have to keep in mind that

anytime in future the next worm incident may be worse. Author observes that the

number of false alarms increase in the case of a DDoS attack or in the case of a hot

website visit. Future work lies in this direction of developing an integrated approach

to further improve the above proposed technique and develop an efficient algorithm

to fight worm attacks.

Security analysts must observe and analyze unusual activity on multiple

firewalls, intrusion detection systems or hosts [11]. A worm might not be positively

identified until it already has spread to most of the Internet, eliminating many

defensive options. In this paper, Authors present an automated system that can

identify active worms seconds or minutes after they first begin to spread, a necessary

precursor to halting the spread of a worm, rather than simply cleaning up afterward.

The implemented system collects ICMP Unreachable messages from instrumented

network routers, identifies those patterns of unreachable messages that indicate

malicious scanning activity, and then searches for patterns of scanning activity that

indicate a propagating worm. In this paper, author examines the problem of active

worms; describe the ICMP-based detection system, and present simulation results.

2.3 OPTIMIZATION

Transmitter power control can be used to concurrently achieve several

key objectives in wireless networking, including minimizing power consumption

and prolonging the battery life of mobile nodes, mitigating interference and

increasing the network capacity and maintaining the required link Quality of Service

(QoS) by adapting to node movements, fluctuating interference, channel

impairments and so on[12]. Moreover, power control can be used as a vehicle for

implementing on-line several basic network operations, including admission control,

channel selection and switching and handoff control. Consider issues associated

with the design of power-sensitive wireless network architectures, which utilize

power efficiently in establishing user communication at required QoS levels.

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Besides reviewing some recent developments in power control, author formulates

some general associated concepts which have wide applicability to wireless network

design. A synthesis of these concepts into a framework for power-sensitive network

architectures is done, based on some key justifiable points. Various important

relevant issues are highlighted and discussed, as well as several directions for further

research in this area. Overall, a first step is taken toward the design of power-

sensitive network architectures for next generation wireless network.

Author has identified a number of key concepts and issues concerning the

potential of adaptive power control in wireless networking. A synthesis of these

concepts has led to a justified framework for power sensitive architectures based on

the Distributed Power Control (DPC)/Active Link Protection (ALP)/Voluntary Drop

Out/Forced Drop Out/Probing suite of algorithms. Important related issues of quick

QoS estimation, power conservation, and so on have also been highlighted. This is a

first step toward designing power sensitive wireless network architectures.

The authors [13] describe the distributed position-based network protocol

optimized for minimum energy consumption in mobile wireless networks that

support peer-to-peer communications. Given any number of randomly deployed

nodes over an area, it illustrates a simple local optimization scheme executed at each

node, guarantees strong connectivity of the entire network and attains the global

minimum energy solution for stationary networks. Due to its localized nature, this

protocol proves to be self-reconfiguring and stays close to the minimum energy

solution when applied to mobile networks.

Applications where minimum energy networking can affect significant

benefits include the digital battlefield, where soldiers are deployed over an

unfamiliar terrain, and multi sensor networks, where sensors communicate with each

other with no base station nearby. Even in the presence of base stations, such as in

cellular phone systems, minimum energy network design can allow longer battery

life and mitigate interference. In this paper, author presents a position-based

algorithm to set up and maintain a minimum energy network between users that are

randomly deployed over an area and are allowed to move with random velocities.

15

Author denotes these mobile users by “nodes” over the two-dimensional plane. The

network protocol reconfigures the links dynamically as nodes move around, and its

operation does not depend on the number of nodes in the system. Simulation results

are used to verify the performance of the protocol.

Span is a power saving technique for multi-hop wireless networks that

reduce energy consumption without significantly diminishing the capacity or

connectivity of the network [14]. Span builds on the observation that when a region

of a shared-channel wireless network has a sufficient density of nodes, only a small

number of them need be on at any time to forward traffic for active connections. It is

a distributed, randomized algorithm where nodes make local decisions on whether to

sleep, or join a forwarding backbone as a coordinator. Each node bases its decision

on an estimate of how many of its neighbors are awake and the amount of energy

available to it. It describes a randomized algorithm where coordinators rotate with

time, demonstrating how localized node decisions lead to a connected, capacity-

preserving global topology. Improvement in system lifetime due to span increases as

the ratio of idle-to-sleep energy consumption increases, and increases as the density

of the network increases. Simulations show that with a practical energy model,

system lifetime of an 802.11 network in power saving mode with Span is a factor of

two better than without. Span integrates nicely with 802.11-when run in conjunction

with the 802.11 power saving mode, Span improves communication latency,

capacity and system lifetime.

Span adaptively elects coordinators from all the nodes in the network, and

rotates them in time. Span coordinators stay awake and perform multi hop packet

routing within the network, while other nodes remain in power saving mode and

periodically check if they should be awaken and become a coordinator

With Span, each node uses a random back off delay to decide whether to

become a coordinator. This delay is a function of the number of the nodes in the

neighborhood that can be bridged using this node and the amount of energy it has

remaining. The results show that Span not only preserves latency, and provides

significant energy savings. For example, for a practical range of node densities and a

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practical energy model, The simulations show that the system lifetime with Span is

more than a factor of two better than without Span.

To build an enterprise network that delivers real value to the business, it's

no longer enough to simply add bandwidth: we have to manage the bandwidth more

effectively than ever before. This book [15] shows how to reduce costs, delay

expenditures, and deliver new applications with precisely service quality they

require. The book explains how to do the following:

1. Understand the technologies and business trends that are driving

service level management in the enterprise network.

2. Learn advanced techniques for differentiating between low-priority

and high-priority applications; then delivering bandwidth in the

appropriate quantities, within appropriate latency and jitter

parameters.

3. Compare Class of Service (CoS) approaches with Quality of

Service (QoS) approaches such as ATM's QoS and Resource

Reservation Protocol for IP networks.

4. Understand how to classify customers and give them preferred

access to Internet and other network resources; handle peak loads

more effectively; delay network upgrades; and much more.

The book includes four detailed case studies representing financial

services, consulting, retail and academic organizations. The definitive guide to

policy-based IP traffic management shows how to guarantee the performance of

mission-critical Internet applications.

Operations Research (OR) is a science which deals with problem,

formulation, solutions and finally appropriate decision making [16]. Scientists and

technocrats form team to study the problem arising out of difficult situations and at

the later stage solutions to these problems. It is the research designed to determine

17

most efficient way to do something new. OR is the use of mathematical models,

statistics and algorithm to aid in decision-making. It is most often used to analyse

complex real life problems typically with the goal of improving or optimizing

performance. Some decisions can be taken by common sense, sound judgment and

experience without using mathematics, and some cases this may not be possible and

use of other techniques is inevitable.

Information is generated in certain nodes and needs to reach a set of

designated gateway nodes [17]. Each node may adjust its power within a certain

range that determines the set of possible one hop away neighbours. Traffic

forwarding through multiple hops is employed when the intended destination is not

within immediate reach. The nodes have limited initial amounts of energy that is

consumed in different rates depending on the power level and the intended receiver.

The author proposes algorithms to select the routes and the corresponding power

levels such that the time until the batteries of the nodes drain-out is maximized. The

algorithms are local and amenable to distributed implementation. When there is a

single power level, the problem is reduced to a maximum �ow problem with node

capacities and the algorithms converge to the optimal solution. When there are

multiple power levels, then the achievable lifetime is close to the optimal (that is

computed by linear programming) most of the time. It turns out that in order to

maximize the lifetime; the traffic should be routed such that the energy consumption

is balanced among the nodes in proportion to their energy reserves, instead of

routing to minimize the absolute consumed power.

The general inverse maximum flow problem is considered [18], where

lower and upper bounds for the flow are changed so that a given feasible flow

becomes a maximum flow and the modification cost that is measured by sum-type

weighted Hamming distance is minimum. Authors present the combinatorial

algorithm for solving the problem that runs in strongly polynomial times.

The minimum cost flow problem with interval data can be solved using

two minimum cost flow problems with crisp data. In this paper, the idea of author

was extended for solving the minimum flow problem with interval-valued lower,

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upper bounds and flows [19]. This problem can be solved using two minimum flow

problems with crisp data. Then, this result is extended to networks with fuzzy lower,

upper bounds and flows.

In this paper, a new method to solve the minimum cost flow problem with

interval data is presented. First, it solves a minimum cost flow problem with lower

bounds, flows, and costs, also a minimum cost flow problem with upper bounds,

flows, and costs. Then, the method combines two solutions as an interval solution.

Author proves that the interval solution is optimal for the minimum cost flow

problem with interval bounds, flows, and costs. In this paper, this idea is extended to

solve the minimum flow problem with interval bounds and flows.

In this paper, author developed the wave preflow algorithm for minimum

flow [20]. This algorithm is a special implementation of the generic preflow

algorithm. It is hybrid between the FIFO preflow algorithm and the highest-label

preflow algorithm for minimum flow. It examines the active nodes in non

decreasing order of their distance labels and the node examination terminates when

either the node deficit becomes zero or the node is relabeled. The wave preflow

algorithm for minimum flow runs in O (n3) time.

The literature on network flow problem is extensive. Over the past 50 years

researchers have made continuous improvements to algorithms for solving several

classes of problems. Researchers designed many of the fundamental algorithms for

network flow, including methods for maximum flow and minimum cost flow

problems. In the next decades, there are many research contributions concerning

improving the computational complexity of network flow algorithms by using

enhanced data structures, techniques of scaling the problem data etc.

2.4 GROUP KEY MANAGEMENT

In this paper author shows how to divide data D into n pieces in such a

way that D is easily reconstructable from any k pieces, but even complete

knowledge of k-1 pieces reveals absolutely no information about D [21]. This

technique enables the construction of robust key management schemes for

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cryptographic systems that can function securely and reliably even when

misfortunes destroy half the pieces and security breaches expose all but one of the

remaining pieces.

The Author generalises the problem to one in which the secret is some

data D (e.g., the safe combination) and in which non mechanical solutions (which

manipulate this data) are also allowed. Author’s goal is to divide D into n pieces D1,

. . . . . D n in such a way that:(1) knowledge of any k or more D i pieces make D

easily computable;(2) knowledge of any k- 1 or fewer Di pieces leaves D completely

undetermined (in the sense that all its possible values are equally likely).Such a

scheme is called a (k, n) threshold scheme.

Group communications can bene�t from IP multicast to achieve scalable

exchange of messages. However, there is a challenge of effectively controlling

access to the transmitted data [22]. IP multicast by itself does not provide any

mechanisms for preventing non group members to have access to the group

communication. Although encryption can be used to protect messages exchanged

among group members, distributing the cryptographic keys becomes an issue.

Researchers have proposed several different approaches to group key management.

These approaches can be divided into three main classes: centralized group key

management protocols, decentralized architectures and distributed key management

protocols. The three classes are described here and an insight given to their features

and goals. The area of group key management is then surveyed and proposed

solutions are classi�ed according to those characteristics.

In this article, authors present a survey in the secure group

communication area, particularly regarding the secure distribution and refreshment

of keying material. Authors review several proposals, placing them into three main

classes: group key management protocols, which try to minimize the requirements

of KDC and group members; decentralized architectures, which divide large group

in smaller subgroups in order to make the management more scalable; and �nally,

the distributed key management protocols, which gives all members the same

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responsibilities. Every class has its particularities, presenting different features,

requirements and goals.

Analysis made it clear that there is no unique solution that can achieve all

requirements. While centralized key management schemes are easy to implement,

they tend to impose an overhead on a single entity. Protocols based on hierarchical

sub grouping are relatively harder to implement and raise other issues, such as

interfering with the data path or imposing security hazards on the group. Distributed

key management, by design, is simply not scalable. Additionally, the best solution

for a particular application may not be best for another, hence it is important to

understand fully the requirements of the application before selecting a security

solution.

WiMAX is the next generation technology that offers broadband wireless

access over long distances [23]. As WiMAX standards expand from considering a

fixed line-of-sight propagation and point-to-multipoint infrastructure high frequency

system to a lower frequency non-line-of-sight mobile system, It is open to more

security threats than other wireless systems. This paper presents the different

security issues present in Privacy and Key Management Protocol along with the

proposed solutions.

Secure group communication has become an important issue in many

applications [24]. Both intra-group and inter-group multicast traffic must be

protected by shared secret keys. In order to communicate securely in the same group

and among different groups, authors employ a polynomial P to achieve efficient

intra-group key refreshment and generate a polynomial H(x) to create an inter-group

key. Proposed polynomial-based key management schemes have the following

advantages: (1) Group members and the group controller can share the intra-group

key without any encryption/decryption. (2) When the members of the group get

changed, the group controller needs to update and distribute the renewed group keys.

The proposed mechanism can reduce the number of re-keying messages. (3) The

proposed mechanism lessens the storage overhead of group members and the group

controller by adopting a polynomial-based key management scheme. (4) As

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compared with previous approaches, the group controller does not need to broadcast

heavy messages which are necessary for creating an inter-group key. Hence, it

introduces only a small amount of broadcast traffic to the group members. The

analysis of the proposed mechanism is conducted to demonstrate the improvements.

Secret sharing scheme is a method which distributes shares of a secret to a

set of participants in such a way that only specified groups of participants can

reconstruct the secret by poling their shares [25]. Secret sharing is related to key

management and key distribution. These problems are common to all crypto

systems. Secret sharing is also used in multi-party secure protocols. Future, secret

sharing schemes have natural applications in access control and cryptographic key

initialization. Key transfer protocols rely on a mutually trusted Key Generation

Center (KGC) to select session keys and transport session keys to all communication

entities secretly.

Mobile ad hoc networks (MANETs) can be defined as a collection of

large number of mobile nodes that form temporary network without aid of any

existing network infrastructure or central access point [26]. Due to the nature of

MANETs, to design and maintaining security is a challenging task for researcher in

an open and distributed communication environment. This paper proposes security

architecture for MANET grid and optimal key management by combining

symmetric key technique and elliptic curve public key technique. The proposed

architecture and optimal key management eliminates threats including the man-in-

the-middle attack and the Black hole attack can be effectively eliminated under the

proposed scheme. Author proposes a scheme which includes strong security,

scalability, fault-tolerance, accessibility, and efficiency.

The demand for an efficient scheme to manage group keys for secure

group communication becomes more urgent [27], as applications of secure multicast

in networks continue to grow. In this paper, authors propose a new key tree structure

for group key management. With this optimal tree structure, system resources such

as network bandwidth can be saved. Authors devise an algorithm to generate this

optimal tree and show that it can be implemented efficiently. Also they design an

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adaptive system for group key management which consists of four components: a

request receiver, a key tree update controller, a delay calculator and a request

predictor. This system can maintain the optimality of the key tree dynamically. It is

verified by theoretical analysis and simulation result that the performance of the

scheme is better than other schemes based on traditional tree structures.

In key management schemes that realize secure multicast communications

encrypted by group keys on a public network, tree structures are often used to

update the group keys efficiently [28]. Authors have proposed an efficient scheme

which updates dynamically the tree structures based on the withdrawal probabilities

of members. In this paper, it is shown that this scheme is asymptotically optimal for

the cost of withdrawal. Furthermore, a new key management scheme, which takes

account of key update costs of joining, in addition to withdrawal, is proposed. The

proposed scheme is also asymptotically optimal, and it is shown by simulation that it

can attain good performance for non asymptotic cases.

2.5 TESLA

Wireless networks will consist of low-powered, compute-constrained

devices [29]. These devices will have limited ability to perform the expensive

computational operations associated with public key cryptography. This will limit

the usefulness of conventional authentication mechanisms based on public key

certificates in these domains. The authors introduce an alternative to conventional

public key certificates that is based upon symmetric key cryptography and the

principles of delayed key disclosure. The work formalizes concepts presented in

earlier work on a broadcast authentication protocol, known as TESLA. TESLA

certificates rely upon a Trade-off between computation and authentication delay in

order to achieve a certificate infrastructure that reduces computational complexity

associated with certificate verification when compared with traditional public key

infrastructure certificates.

A wireless network has one or more base stations that talk to a large set of

wireless sensors, where the wireless life depends on a small battery that consumes

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most power during communication [30]. Before this network can be applied, many

security problems must be solved, yet traditional security protocols usually need a

lot of communication overhead.

Secure group communication has become an important issue in many

applications. Both intra-group and inter-group multicast traffic must be protected by

shared secret keys [31]. In order to communicate securely in the same group and

among different groups, it employs a polynomial P to achieve efficient intra-group

key refreshment and generate a polynomial H(x) to create an inter-group key.

Proposed polynomial-based key management schemes have the following

advantages: (1) Group members and the group controller can share the intra-group

key without any encryption/decryption. (2) When the members of the group get

changed, the group controller needs to update and distribute the renewed group keys.

The proposed mechanism can reduce the number of re-keying messages. (3) The

proposed mechanism lessens the storage overhead of group members and the group

controller by adopting a polynomial-based key management scheme. (4) As

compared with previous approaches, the group controller does not need to broadcast

heavy messages which are necessary for creating an inter-group key. Hence, it

introduces only a small amount of broadcast traffic to the group members. The

analysis of the proposed mechanism is conducted to demonstrate the improvements.

The contributions of the proposed schemes are: (1) Sharing the intra-group key

between the group controller and group members do not need to adopt any

encryption/decryption mechanisms. (2) When membership changes happen, the keys

are renewed immediately. The designed mechanism reduces the number of re-

keying messages during group membership changes. (3) The adoption of the

polynomial which is used for deriving an intra-group key can reduce the key storage

overhead at the group members and the group controller. (4) After the intra-group

key is derived, the members self generate the polynomial functions which are

necessary for creating an inter-group key. It helps to reduce the communication

overhead at the group controller.

The TESLA multicast stream authentication protocol is distinguished

from other types of cryptographic protocols in both its key management scheme and

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its use of timing [32]. It takes advantage of the stream being broadcast to

periodically commit to and later reveal keys used by a receiver to verify that packets

are authentic, and it uses both inductive reasoning and time arithmetic to allow the

receiver to determine that an adversary cannot have prior knowledge of a key that

has just been revealed. While an informal argument for the correctness of TESLA

has been published, no mechanized proof appears to have previously been done for

TESLA or any other protocol of the same variety. This paper reports on a

mechanized correctness proof of the basic TESLA protocol based on establishing a

sequence of invariants for the protocol using the tool TAME. It discusses the

organization and process used in the proof, and the possibilities for reusing these

techniques in correctness proofs of similar protocols, starting with more

sophisticated versions of TESLA.

The present strategies that reduce the delay associated with multicast

authentication, make more efficient usage of receiver-side buffers, make delayed

key disclosure authentication more resilient to buffer overflow denial of service

attacks, and allow for multiple levels of trust in authentication [33]. Throughout this

base paper, the main focus of discussion will be on the popular multicast

authentication scheme Timed Efficient Stream Loss-tolerant Authentication

(TESLA) based upon the delayed key disclosure principle. Similar to other schemes

based upon delayed key disclosure, TESLA is susceptible to Denial-of-Service

(DoS) attacks and is not well suited for delay-sensitive applications.

The Internet of Things (IoTs) is an emerging concept referring to

networked everyday objects that interconnect to each other via wireless sensors

attached to them [34]. TESLA is a source authentication protocol for the broadcast

network. Scalability of TESLA is limited by distribution of its unicast-based initial

parameter. Low energy consumption version of TESLA is �TESLA, which is

designed for wireless sensor network (WSN), while cannot tolerate DoS attack.

TESLA++ is the DoS-tolerant version and is designed for VANET. TESLA++

cannot be accepted by WSN because of its higher consumption of power. To realize

secure and robust DoS attack in the hybrid-vehicle-sensor network, author provides

a TESLA-based protocol against DoS attack with a lower consumption of power.

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Analysis results demonstrate that using this protocol is better than using �TESLA or

TELSA++, respectively

Author summarizes the soft verification of message protected by

symmetric cryptographic check values, i.e. Message Authentication Codes [35]. Soft

verification is introduced as an extension of hard or standard verification, which is

usual today in cryptographic applications. Algorithm for iterative correction of

messages protected by Message Authentication Codes is theoretically analyzed,

using probability theory. Results of the analysis are used for defining the most

important parameter for the correct work of the algorithm – a threshold value.

Theoretical analysis is also used for comparison with results of simulations of the

threshold value used in the algorithm for soft verification. Similar results of the

comparison confirm the theoretical analysis. At the end of the paper, simulation

results and considerable gain of corrected messages and their Message

Authentication Codes is shown.

Authenticated key exchange protocols allow two participants A and B,

communicating over a public network and each holding an authentication means, to

exchange a shared secret value [36]. Methods designed to deal with this

cryptographic problem ensure A (resp. B) that no other participants aside from B

(resp. A) can learn any information about the agreed value, and often also ensure A

and B that their respective partner has actually computed this value. A natural

extension to this cryptographic method is to consider a pool of participants

exchanging a shared secret value and to provide a formal treatment for it. Starting

from the famous 2-party Diffie-Hellman (DH) key exchange protocol, and from its

authenticated variants, security experts have extended it to the multi-party setting for

over a decade and completed a formal analysis in the framework of modern

cryptography in the past few years. This paper synthesizes the body of work on the

provably-secure authenticated group DH key exchange.

In this paper author has provided a formal model and security definitions,

as well as methods, for authenticated group Diffie-Hellman key exchange. This

work should allow cryptographic experts to properly analyze the security of a group

26

key exchange protocol, to address in a rigorous way the security requirements a

given method aims to achieve, and to come up with provably secure protocols. The

proposed model is sufficiently generic to be adapted to many cryptographic

scenarios well-suited for key exchange in a group. In addition, performed a security

analysis a protocol suite already proposed for dynamic group Diffie-Hellman key

exchange; enhanced it with authentication services, proposed a modular

implementation that can be used to abstract out the use of cryptographic devices, and

exhibit a formal security proof under standard computational assumptions. This

paper, will enable security architects to pick a method based not only on its

efficiency but also on its (provable) security.

One of the main challenges of securing multicast communication is

source authentication, or enabling receivers of multicast data to verify that the

received data originated with the claimed source and was not modified enroute [37].

The problem becomes more complex in common settings where other receivers of

the data are not trusted, and where lost packets are not retransmitted. Several source

authentication schemes for multicast have been suggested in the past, but none of

these schemes is satisfactorily efficient in all prominent parameters. Authors have

recently proposed a very efficient scheme, TESLA, which is based on initial loose

time synchronization between the sender and the receivers, followed by delayed

release of keys by the sender. This paper proposes several substantial modifications

and improvements to TESLA. One modification allows receivers to authenticate

most packets as soon as they arrive (whereas TESLA requires buffering packets at

the receiver side and provides delayed authentication only). Other modifications

improve the scalability of the scheme, reduce the space overhead for multiple

instances, increase its resistance to denial-of-service attacks.

The basic TESLA protocol has the following salient properties:

� Low computation overhead. On the order of one MAC function

computation per packet for both sender and receiver.

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� Low communication overhead. Required is as little as one MAC

value per packet. Periodically, the sender also needs to send out the

secret keys.

� Perfect loss robustness. If a packet arrives in time, the receiver can

verify its authenticity eventually (as long as it receives later packets).