This book constitutes the refereed post-conference proceedings of the 17th EAI International Conference on Quality, Reliability, Security and Robustness in Heterogeneous Networks, QShine 2021, held in November 2020.Due to COVID-19 pandemic the conference was held virtually. The 20 revised full papers were carefully reviewed and selected from 43 submissions.The papers are organized thematically in tracks Machine Learning in Distributed Networks; 5G Networks and Security; IoT Security and Lightweight Cryptography; Network Security; and Privacy-preserving Emerging Networked Applications.