This book constitutes the refereed proceedings of the 21st International Conference on Cryptology and Network Security, CANS 2022, which was held during November 13-16, 2022. The conference was took place in Abu Dhabi, United Arab Emirates.The 18 full and 2 short papers presented in these proceedings were carefully reviewed and selected from 54 submissions. They were organized in topical sections as follows: zero-knowledge and MPC; public-key infrastructure; attacks and countermeasures; cryptanalysis and provable security; cryptographic protocols; blockchain and payment systems; and codes and post-quantum cryptography.