With the advent of smart devices and the predominance of open platforms, security problems have been complicated and pivotal to security critical services such as mobile payment and banking, etc. While hardware technologies have been suggested to tackle this problem, we focus on the software-based approach. In this paper, we propose a secure execution environment that is designed to offer security service from a closed domain. We take advantage of virtualization to create two separate domains with different security policies. Specifically, we describe the major design principles and the important aspect of service model. We expect that our framework will motivate the research for improving the secure execution environment and expand the extent which the smart device can be utilized.