The LNCS 13172 constitute the proceedings of the 13th International Symposium on Cyberspace Safety and Security, CSS 2021, held online, in November 2021.The 9 full papers and 5 short papers presented in this book were carefully reviewed and selected from 35 submissions.

Encrypted Malicious Traffic Detection Based on Ensemble Learning.- A Federated Learning Assisted Conditional Privacy Preserving Scheme for Vehicle Networks.- Dissecting Membership Inference Risk in Machine Learning.- Webshell Detection Based on Explicit Duration Recurrent Network.- A Practical Botnet Traffic Detection System using GNN.- Vulnerability and Transaction behavior based detection of Malicious Smart Contracts.- A novel method of template protection and two-factor authentication protocol based on biometric and PUF.- Realizing Information Flow Control in ABAC Mining.- Weak Password Scanning System for Penetration Testing.- Environmental Adaptive Privacy Preserving Contact Tracing System for Respiratory Infectious Diseases.- A Privacy-Preserving Logistics Information System with Traceability.- Post-quantum Key Escrow for Supervised Secret Data Sharing on Consortium Blockchain.- Flexible and Survivable Single Sign-On.- The Analysis and Implication of Data Deduplication in Digital Forensics.