Research On Trust Management And Its Application In Protecting Mobile Ad Hoc Networks

Trust management is a new information security mechanism derived from the complex trust relationships in human society.It solves the problem of dynamic trust among entities in distributed systems or networks.Trust management involves with collecting trust related information,modeling and evaluating trust relationships,and trust based decisions.Trust management is particularly suitable for protecting the security of distributed and dynamic networks and applications,such as mobile ad hoc networks(MANET),wireless sensor networks(WSN)and E-commerce.MANET is one of the environments in which trust management is mostly applied,and it has become a research hotspot.MANET is a kind of distributed network that does not require fixed network infrastructures.Its capability of fast deployment makes MANET very potential to be used in battlefield communications,disaster rescue,etc.However,because of its highly dynamic topology,open wireless links,and constrained computing resources of mobile nodes,MANET is vulnerable to various attacks.Traditional cryptographic schemes such as confidentiality and authentication mechanisms are invalid for dynamic security,while trust management is able to provide dynamic protection.Despite its advantages,the research of the basic theory of trust management is still at a very early stage,and there are still many problems of trust models,trust based routing and deployment of trust-based mechanisms in applying trust management to protecting MANET.To solve these problems,we conduct in-depth research in this paper.This paper aims to research some problems of the basic theory of trust management,design direct and indirect trust models to evaluate the trust value of entities,and establish trust management systems to effectively protect MANET based on the above models.Main works and contributions of this paper include: 1.The definition and property of trust,and the trust management framework are researched.Based on the development of trust management,advantages and disadvantages of prior definitions of trust are analyzed.On this basis,we propose a definition of trust and its formalized description.Then we summarize the widely accepted properties of trust,and discuss the controversial viewpoints of some properties.At last,an effective trust management framework is proposed.2.Two direct trust models are proposed,one is based on fuzzy Petri net,and another one is based on fuzzy logic and graph theory.Advantages of the first model are: the trust reasoning algorithm is based on matrix operation,which enhances the computational efficiency;reasoning rules in competitive mode are introduced,which makes fuzzy Petri net more suitable for evaluating trustworthiness.Advantages of the second model are: it is able to describe vague knowledge in a formalized way;it is very applicable for distributed networks;a simple but efficient trust value decay algorithm is proposed and built in.3.A similarity based indirect trust model is proposed.This model overcomes the shortcoming of current models that trust recommendations are distorted due to the improper decay,and is able to detect spoofed recommendations.To establish the model,we first design an approach for calculating trust model similarity.This approach exploits the one-hop relationship between trustors and recommenders,and overcomes the challenge of measuring similarity in multi-hop recommendations.Then,a simple but effective spoofed recommendation detection algorithm is proposed.The proposed indirect trust model is general.In other words,it can not only be applied in MANET but also can be integrated into the trust management systems of other types of networks.Simulation results show that compared with existing indirect trust models,the indirect trust value calculated by the proposed model is closer to the real trust value.4.A trust based routing algorithm is proposed.This algorithm is able to select a path with the maximum path trust value among all possible paths between any two end nodes.Moreover,its correctness is proved.Then,we integrate the algorithm into the OLSR protocols by modifying the message formats and developing policy of transmitting trust information,and then we obtain two trust based routing protocols,FGT-OLSR and FPNT-OLSR.Simulation results show that the two protocols perform better on defending against attacks and improving network performance.5.Two trust factor collection methods are proposed.The first one is based on overhearing.We describe the details of information collection in a formalized way.Considering that overhearing may be invalid in some situations,we propose another collection method which is based on acknowledgement.6.Based on the proposed trust models,trust based routing algorithm and the collection methods of trust factors,we establish the trust management system(TMS)that is able to protect the security of both data plane and control plane of MANET.To ensure the implementation and deployment of TMS,we design a deployment scheme.The scheme encapsulates the security primitives such as trust management mechanism and message authentication into a module that is relatively independent of the host router and is self-protected.7.Finally,we conduct many simulation tests to verify the effectiveness of the proposed models,algorithms and systems in protecting the security of MANET.The results show the mechanisms proposed in this paper are effective in defending against various attacks and improving the network performance.