Research On Subjective Trust Management Based On Uncertainty Theory Under Open Network Environment

With the rapid development of open network technology, network services model along also undergone a major shift, network environment from the closed-oriented, the familiar user groups and relatively static form into open, public, height dynamic. In the open network environment emerging more and more network applications, compared to traditional network environment, security needs are endless, traditional security mechanisms based on registration, authentication and authorization is incompetent for this. To this end, there is a problem that urgent need be to address, that is, to assess the credibility of the many participants in the network environment, as well as its service capabilities, service level judge. This requires the use of a new, more flexible security mechanism, which is security mechanism based on trust. There are two main types of trust-based security mechanisms:objective trust-based security mechanisms and security mechanisms based on the subjective trust. This study is the subjective trust-based security mechanisms.According to the mathematical tools used, the current subjective trust model is divided into two categories:trust model based on probability theory and trust model based on fuzzy set theory. In the course of the study of most of the existing trust model, taking into account only the subjectivity of trust, using a probability-based method to calculate the trust, naturally, the vagueness of the trust is ignored. And because of the trust as a static process, and therefore lead to the dynamic nature of the trust is ignored. Even though some researchers have come to realize the trust vagueness also started some research. However, the study is too simple and not deep enough, and fuzzy theory has been applied only in a trust model application without full swing.However, the subjective trust relationship in the open network environment is an uncertain relationship to the dual characteristics of both ambiguity and uncertainty. Therefore, during the subjective trust management need balance between these two features. The subjective trust model based on probability theory and fuzzy set theory was put forward by many researchers did not do it. To this end, the new uncertainty analysis theory that is set pair analysis and cloud model is introduced into the study of subjective trust, in order to solve the ambiguity and uncertainty problem in the trust expression, and propose a trust model based on uncertainty theory which is suitable for open network environment.The main contributions of the work are as follows:1. The main features of experience and lack on trust model of number of researchers carried out a full analysis. On this basis, clearing definition of trust, the classification of the trust, the specific factors influence trust, the main features of trust, the characteristics of both sides of trust relationship in open network environment, analysis the difficulties faced by the trust model, and the need to address problems.2. In order to express trust, the trust contact number was use to represent the trust relationship between the nodes, can fully reflect the subjectivity, uncertainty, and dynamic etc. essential characteristics between nodes in open network, the most basic research was made for in the future trust research in open network environment.3. For subjective characteristics of trust, a multi-dimensional trust model based on cloud model was proposed. The model is derived from random mathematics and fuzzy mathematics and has a solid theoretical foundation and reasonable semantic interpretation through theoretical analysis and simulation. Therefore, we can effectively deal with the subjectivity problem of trust.4. Set pair analysis theory was introduced into the research of trust model, a P2P network anti-attack trust model based on contact numbers was proposed. By analysis of simulation experiments, the model has a good resistance to aggressive. In addition, the multivariate connection number was introduced into subjective trust evaluation and decision-making in open network, the evaluation and decision-making of multi-language variables of trust can better be solved. Meanwhile, through analysis and simulation experiments show that the trust model based on contact number can effectively deal with the uncertainty of subjective trust in the open network environment.5. The cloud model was introduced into a trust model, and a multi-dimensional grid trust model based on cloud model was proposed, can solve the grid trust multi-attribute description, transfer, merger, update, assessment and decision-making, suppress and eliminate the open network services fraud, improve the quality and reliability of the service, and achieve the purpose to improve the overall system availability.