The present book includes extended and revised versions of a set of selected papers presented at the 18th International Joint Conference on e-Business and Telecommunications, ICETE 2021, held as an online web-based event (due to the COVID-19 pandemic) in July 2021. The 17 full papers included in this book were carefully reviewed and selected from 197 submissions. They were organized in topical sections as follows: e-Business and security and cryptography.