Cybersecurity for the IoT ecosystem, which has attracted tremendous attention from academia and industry, plays an essential role in protecting IoT devices and their collected sensitive data. Among many security aspects, effective device authentication and efficient, secure communication play key roles in building a strong cybersecurity framework for IoT devices. Therefore, this project aims to provide a holistic design for a cyber-secure and efficient data communication framework for supporting massive IoT devices. Specifically, we first propose an effective authentication system to manage the identities of IoT devices by employing customized lightweight certificates for IoT devices and developing methods to speed up the authentication process. We take different security requirements from IoT devices and their users to provide graded security levels on the authentication system. This enables users to have the flexibility to choose those devices and pay for the security service. Second, we develop a secure and efficient data communication framework based on the authentication system for communication and data sharing. We also consider common vulnerabilities on IoT devices, such as compromised devices due to a lack of secure update mechanisms and privacy leakage. And we incorporate methods to discover and mitigate these vulnerabilities into our designs. Finally, we provide thorough plans to evaluate our proposed framework.