This paper provides an overview of security basics, feature requirements, technical solutions, and associated system-level trade-offs for implementing security in IoT devices. Making the required trade-offs is significantly easier by leveraging secure, proven building blocks that were designed with secure systems in mind and optimized for low footprint and energy. This paper can help you decide on the optimal mix of features and best trade-offs to make for your specific IoT device, resulting in an efficiently implemented and secure architecture.