Mandatory Access Control Models Research For Important Information System

As everyone knows, the primary goals of information security are confidentiality, integrity and availability. To avoid information leak is one of the most important things for government agencies, armies and enterprises. Mandatory access control can provide better security than discretionary access control. According to information system classified protection of China, information systems which have higher security levels than three must support mandatory access control. Mandatory access control has formed and developed for forty years. However, the uppermost problem is that the access rules are too rigid.This paper focuses on important information systems with third or higher security level. Based on classic mandatory access control model ---BLP model, this paper concentrates on flexibility and security of mandatory access control model. Four mandatory access control models are proposed for different requirements. The flexibility of model is greatly improved under the premise of security. The main contents of this thesis are as follows:(1) According to special requirements of electronic documents in important information system and referencing to the rules of State Secrets Law that state secrets must be attached confidentiality period, a time limit based mandatory access control model (TLBMAC) is proposed which takes the confidentiality period as a property of access control model. The new property is called protection period. In this model, security levels of objects can be adjusted through protection period, which makes the security levels of objects degraded in time. Through setting protection period, non-sensitive information can flow from high security levels to low security levels. In the meantime, objects are classified into different types which can provide better protection for important objects. The security of model is proved by state machine.(2) The emergence of new technologies provides better support for access control. A temporal-spatial-based access control model (TSBMAC) is proposed which integrates positioning technology and trusted computing technology. For critical applications with high security requirements, solely relying on the logical access control is insufficient to provide adequate security. It is essential to confine the security of access environment. TBMAC model integrates time, location and platform constraints through which logical access control is combined with physical environment to provide better security guarantee. In the meantime, the storage locations of objects are confined to avoid information leak through unsafe platform.(3) Integrated subject-object-view access control with task-view access control, a collaboration supported mandatory access control model (CSMAC) is proposed. This model meets the features of active security model. In the model, static, short-term and task irrelevant privileges are linked with dynamic, long-term and task relevant privileges. The model meets the access control requirements of collaboration environment and it benefits to solve the difficult problem of confined bi-directional information flow. In this paper, a noninterference model corresponding to CSMAC model is established and security of model is proved through noninterference theory.(4) Based on TSBMAC model and CSMAC model, we propose a temporal-spatial-based mandatory access control model in collaborative environment (CETSMAC). This model constrains the access from time and space. Furthermore, the time and space constrains can overlap task domain which assures that the implementation of task satisfies the requirements of time and physical environment. This model is applicable to collaborative environment with location-aware. The security of model is proved by noninterference theory.In a word, this paper takes the confidentiality of important information system as target to research mandatory access control model. To improve the flexibility and security of mandatory access control model, different mandatory access control models are proposed to meet different security requirements. This work is useful for promoting the construction of information security classified protection and provides new idea for ensuring confidentiality of important information system.