This book constitutes the refereed proceedings of the 20th International Conference on Provable Security, ProvSec 2026, held in Queenstown, New Zealand, during September 24–26, 2026.

The 19 full papers, 4 short papers included in this book were carefully reviewed and selected from 66 submissions. They were organized in topical sections as follows: Machine Learning Security and Privacy,Machine Learning for Security Applications,Database Security,Blockchain and Cryptocurrency,Signatures and Watermarking,Encryption Schemes and Short papers.