This book constitutes the refereed proceedings of the 15th International Symposium on Foundations and Practice of Security, FPS 2022, held in Ottawa, ON, Canada, during December 12–14, 2022.The 26 regular and 3 short papers presented in this book were carefully reviewed and selected from 83 submissions. The papers have been organized in the following topical sections: Cryptography; Machine Learning; Cybercrime and Privacy; Physical-layer Security; Blockchain; IoT and Security Protocols; and Short Papers.