This book constitutes the revised selected papers of the 18th International Conference, SecITC 2025, held in Bucharest, Romania, during November 20–21, 2025.

The 20 full papers included in this volume were carefully reviewed and selected from 44 submissions. They are organized in the following topical sections: Cryptographic Primitives and Protocols; Post-quantum Cryptography; Artificial Intelligence Techniques for Security; Application, System and Network Security.