This book constitutes the refereed proceedings of the 38th IFIP TC 11 International Conference on Information Security and Privacy Protection, SEC 2023, held in Poznan, Poland, in June 2023. The 26 full papers included in this book were carefully reviewed and selected from 84 submissions. They focus on topics such as access control and authentication; applied cryptography; mobile security; side-channel attacks; trust management, digital forensics; industry networks security, etc. .