The LNCS volume 13269 constitutes the proceedings of the 20th International Conference on Applied Cryptography and Network Security, ACNS 2022, which will take place in a hybrid mode in Rome, Italy in June 2022. The 44 full papers together with 5 short papers presented in this proceeding were carefully reviewed and selected from a total of 185 submissions. They were organized in topical sections as follows: Encryption, Attacks, Cryptographic Protocols, System Security., Cryptographic Primitives, MPC, Blockchain, Block-Cyphers, and Post-Quantum Cryptography.