This book constitutes revised selected papers from the 11th International Workshop on Constructive Side-Channel Analysis and Secure Design, COSADE 2020, held in Lugano, Switzerland, in April 2020.

Due to COVID-19, the workshop was held online.

The 15 papers presented in this volume were carefully reviewed and selected from 36 submissions. The workshop covers subjects from wide ranges such as secure design, side channel attacks and countermeasures, and architectures and protocols.