This book constitutes the refereed proceedings of the 20th International Conference on Information and Communications Security, ICICS 2018, held in Lille, France, in October 2018.

The 39 revised full papers and 11 short papers presented were carefully selected from 202 submissions. The papers are organized in topics on blockchain technology, malware, botnet and network security, real-world cryptography, encrypted computing, privacy protection, signature schemes, attack analysis and detection, searchable encryption and identity-based cryptography, verifiable storage and computing, applied cryptography, supporting techniques, formal analysis and cryptanalysis, attack detection, and security management.