The 21st International Conference on Information Security and Cryptology (INSCRYPT 2025) will be held in Xi’an from October 19th to October 21st, 2025, organized by the State Key Laboratry of Integrated Services Networks (ISN) of Xidian University and the State Key Laboratory of Cyberspace Security Defense (SKLCSD) of the Institute of Information Engineering of Chinese Academy of Science. Inscrypt 2025 seeks high-quality research contributions in the form of well developed papers. Topics of interest encompass research advances in ALL areas of information security, cryptology, and their applications. The conference proceedings will be published by Springer-Verlag in LNCS series.