This book constitutes the proceedings of the 3rd International Conference on Data Security and Privacy Protection, DSPP 2025, held in Xi'an, China, during October 16–18, 2025.The 36 full papers and 11 short papers presented in these two volumes were carefully reviewed and selected from 105 submissions.The papers are organized in the following topical sections:Part I:AI and System Security; Blockchain and Related Technologies; Privacy Preserving/Enhancing Technologies; Cryptographic Primitives; Privacy-Aware Federated Learning; AI-based Security Applications and Technologies.Part II: AI-based Security Applications and Technologies; Cryptographic Protocols Design and Analysis; Model Security and Copyright Protection.