Full papers -- RLTree: Website Fingerprinting through ResourceLoading Tree -- Re-check Your Certificates! Experiences and Lessons Learnt from Real-world HTTPS Certificate Deployments -- ZERMIA - A Fault Injector framework for testing Byzantine Fault Tolerant protocols -- Revocable Data Sharing Methodology Based on SGX and Blockchain -- On the Analysis of the Outsourced Revocable Identity-Based Encryption from Lattices -- Preventing Fake News Propagation in Social Networks using a context Trust-based security model -- A Lightweight Android Malware Detection Framework based on Knowledge Distillation -- Federated learning-based intrusion detection in the context of IIoT networks: Poisoning Attack and defense -- A Simplified and Effective Solution for Hybrid SDN Network Deployment -- Group Key Exchange Compilers from Generic Key Exchanges -- An architecture for processing a dynamic heterogeneous information network of security intelligence -- The Complexity of Testing Cryptographic Devices on Input Faults -- A Malware Family Classification Method Based on the Point Cloud Model DGCNN -- Collection of the main Anti-Virus detection and bypass techniques -- Profiled Attacks against the Elliptic Curve Scalar Point Multiplication using Neural Networks -- Deep Cross-modal Supervised Hashing based on Joint Semantic Matrix -- Short papers -- Accurate Polar Harmonic Transform-based Watermarking Using Blind Statistical Detector -- Cloud Key Management Based on Verifiable Secret Sharing -- A Scheme for Sensor Data Reconstruction in Smart Home -- Privacy-preserving and Auditable Federated Deep Reinforcement Learning for Robotic Manipulation -- HALNet: A Hybrid Deep Learning Model for Encrypted C&C Malware Traffic Detection -- Tracing Software Exploitation -- A Secure and Privacy Preserving Federated Learning Approach for IoT Intrusion Detection System -- Cryptanalysis of A Fully Anonymous Group Signature with Verifier-Local Revocation from ICICS 2018.

This book constitutes the refereed proceedings of the 15th International Conference on Network and System Security, NSS 2021, held in Tianjin, China, on October 23, 2021. The 16 full and 8 short papers presented in this book were carefully reviewed and selected from 62 submissions. They focus on theoretical and practical aspects of network and system security, such as authentication, access control, availability, integrity, privacy, confidentiality, dependability and sustainability of computer networks and systems.