Fast growth in a number of connected devices, heterogeneity, constrained resources, privacy, software upgrades and operational environment create important security related challenges in Internet of Things (IoT) domain. In this research, a literature survey of the state of the art is conducted related to security aspects. The results are validated by conducting qualitative interviews with IoT practitioners. The efforts have resulted towards identifying several security trends and challenges and some design aspects to be considered by IoT practitioners. The outcomes point towards that security is not only a technical problem but is more of an awareness, mindset, people and process issue. In this paper, a novel model is conceptualized with openness and security characteristics followed with several key aspects important to design an IoT system. This model emphasizes the human in the loop aspect, which would help to determine the dynamic requirements and design principles of IoT systems in a more open, common and secure way.