Stability of Software Trustworthiness Measurements Models

The software trustworthiness is an important feature for the safety and security of cyber-physical system. Therefore, how to assess software trustworthiness is the key issue. Tao has recently given five measurement models of software trustworthiness based on the attributes of software in his Doctoral Dissertation and his publications. After simulating these models with the Monte Carlo method, we find out that these models have a common shortcoming that the trustworthy degree would not be within the same range as the range in which all attributes´ values are. In order to solve this problem, this paper introduces the stability rule with which measurement model of software trustworthiness is proposed. According to these rules, this paper proposes two models which are originally based on Tao´s models. The succeeding mathematical proof and simulation demonstrate that these models meet all the rules. These two models have been applied to compute the degree of software trustworthiness in the software trustworthy measurement and evaluation tool.