In the decentralized and highly dynamic environment like Mobile Pervasive Environments (MPE) trust and security measurement are two major challenging issues for community researchers. So far primarily many of architectural frameworks and models developed and being used. In the vision of pervasive computing where mobile applications are growing immensely with the potential of low cost, high performance, and user centric solutions. This paradigm is highly dynamic and heterogeneous and brings along trust and security challenges regarding vulnerabilities and threats due to inherent open connectivity. Despite advances in the technology, there is still a lack of methods to measure the security and level of trust and framework for the assessment and calculation of the degree of the trustworthiness. In this paper, we explore security and trust metrics concerns requirement and challenges to decide the trust computations metric parameters for a self-adaptive self-monitoring trust based security assurance in mobile pervasive environment. The objective is to identify the trust parameters while routing and determine the node behavior for soft security trust metric. In winding up, we put our efforts to set up security assurance model to deal with attacks and vulnerabilities requirements of system under exploration.