Access Control in Safety Critical Environments

This paper describes an access control system for industrial automation and control systems (IACS) and similar automation systems for smart energy grids. The intended area of applications of the proposed system are control/station and substation networks to protect connected devices and associated safety relevant settings from unauthorized access. The proposed solution for access control introduces a two-stage access control schema. The first stage evaluates policies based on the eXtensible access control markup language (XACML) and the second stage uses knowledge about the system's behavior to prevent malicious or accidental operations that have negative impact on the systems stability. The access control system uses RFC 5755 attribute certificates to store properties of subjects, resources, rsp. objects and system information. The design and implementation of the system considers safety requirements such as timing requirements or availability in order to enable an integration in safety-critical environments.