Cryptographic Protocols -- Adaptive-ID Secure Hierarchical ID-Based Authenticated Key Exchange under Standard Assumptions without Random Oracles -- Analysis of Client-side Security for Long-term Time-stamping Services -- Towards Efficient and Strong Backward Private Searchable Encryption with Secure Enclaves -- Secure and Fair Protocols -- CECMLP: New Cipher-Based Evaluating Collaborative Multi-Layer Perceptron Scheme in Federated Learning -- Blind Polynomial Evaluation and Data Trading -- Coin-Based Multi-Party Fair Exchange -- Cryptocurrency and Smart Contracts -- P2DEX: Privacy-Preserving Decentralized Cryptocurrency Exchange -- WOTS+ up my Sleeve! A Hidden Secure Fallback for Cryptocurrency Wallets -- Terrorist Attacks for Fake Exposure Notifications in Contact Tracing Systems -- Digital Signatures -- Unlinkable and Invisible -Sanitizable Signatures -- Partially Structure-Preserving Signatures: Lower Bounds, Constructions and More -- An Efficient Certificate-Based Signature Scheme in the Standard Model -- Embedded System Security -- SnakeGX: a sneaky attack against SGX Enclaves -- Telepathic Headache: Mitigating Cache Side-Channel Attacks on Convolutional Neural Networks -- Efficient FPGA Design of Exception-Free Generic Elliptic Curve Cryptosystems -- Lattice Cryptography -- Access Control Encryption from Group Encryption -- Password Protected Secret Sharing from Lattices -- Efficient Homomorphic Conversion Between (Ring) LWE Ciphertexts.

The two-volume set LNCS 12726 + 12727 constitutes the proceedings of the 19th International Conference on Applied Cryptography and Network Security, ACNS 2021, which took place virtually during June 21-24, 2021. The 37 full papers presented in the proceedings were carefully reviewed and selected from a total of 186 submissions. They were organized in topical sections as follows: Part I: Cryptographic protocols; secure and fair protocols; cryptocurrency and smart contracts; digital signatures; embedded system security; lattice cryptography; Part II: Analysis of applied systems; secure computations; cryptanalysis; system security; and cryptography and its applications.