The deployment of small handheld devices in a pervasive environment inevitably raises security concerns while sharing services. Trust models play a major role in guarding against privacy violations and security breaches. Though assignment of initial trust is an important issue, little work has been done in this area. Most of the prior research on trust models assume a constant level of the initial trust value. However, in a pervasive smart space, trust is context dependent. The need for security varies from context to context. In addition, some services, being shared in this environment, require high security while sharing. To ensure this, security levels should be incorporated in the initial trust calculation. In this paper, we propose a new initial trust model called ICSTB (Integration of Context Security in Trust Bootstrapping). The model categorizes services or contexts in different security levels based on their security needs, and these security needs are considered in trust bootstrapping.