SecureComm is a conference in EAI core conference portfolio focusing on cybersecurity. The aim of SecureComm is to bring together researchers and practitioners in academic, industry, and government in security, networking, communication and other related communities to explore important research directions in the field. The 21st SecureComm conference seeks submissions of high-quality research contributions. Topics of interest encompass ALL areas of secure communications and networking. Topics in less related areas will be considered if a clear connection to secure communication and networking is demonstrated. Topics addressing interdisciplinary challenges in different application domains are welcome.