This three-set volume LNCS 16217-16219 constitutes the refereed proceedings of 27th International Conference on Information and Communications Security, ICICS 2025, held in Nanjing, China, during October 29-31, 2025.

The 91 full papers presented in this book were carefully selected and reviewed from 357 submissions. The papers are organized in the following topical sections:

Part I: Cryptography; Post-quantum Cryptography; Anonymity and Privacy; Authentication and Authorization.

Part II: Blockchain and Cryptocurrencies, System and Network Security, Security and Privacy of AI, Machine Learning for Security.

Part III: Attack and Defense; Vulnerability Analysis; Anomaly Detection; Traffic Classification; Steganography and Watermarking.