This two-volume set, LNCS 14905-14906, constitutes the proceedings from the 23rd International Conference on Cryptology and Network Security, CANS 2024, held in Cambridge, United Kingdom during September 24-27, 2024.  The 25 papers included in these volumes were carefully reviewed and selected from 76 submissions. The papers presented in these two volumes are organized in the following topical sections:-Part I: Multi-party Computation; Post-quantum Security; Anonymity and Privacy; Blockchain Technology. Part II: Cyber Security and Leakage; Machine Learning and Security; Provable Security; Cryptanalysis.