This book constitutes the proceedings from the 24th International Conference on Cryptology and Network Security, CANS 2025, held in Osaka, Japan during November 17–20, 2025.The 26 full papers and 7 short papers were carefully reviewed and selected from 81 submissions. They are organized in topical sections as follows: Post-Quantum Cryptography; Symmetric-Key Cryptography; Multi-Party Computation; Advanced Encryption; Cryptographic Protocols and Blockchain; Vulnerability Detection; and Attacks.