Book excerpt: This book constitutes revised selected papers from the 21st International Conference on Information Security and Cryptology, ICISC 2018, held in Seoul, South Korea, in November 2018. The total of 21 papers presented in this volume were carefully reviewed and selected from 49 submissions. The papers were organized in topical sections named: public-key encryption and implementation; homomorphic encryption; secure multiparty computation; post-quantum cryptography; secret sharing and searchable encryption; storage security and information retrieval; and attacks and software security.