Symmetric Designs -- Ciminion: Symmetric Encryption Based on Toffoli-Gates over Large Finite Fields -- Mind the Middle Layer: The HADES Design Strategy Revisited -- Password Hashing and Preprocessing -- Compactness of Hashing Modes and Efficiency beyond Merkle Tree -- Real-World Cryptanalysis -- Three Third Generation Attacks on the Format Preserving Encryption Scheme FF3 -- Cryptanalysis of the GPRS Encryption Algorithms GEA-1 and GEA-2 -- Implementation Issues -- Pre-Computation Scheme of Window NAF for Koblitz Curves Revisited -- Dummy Shuffling against Algebraic Attacks in White-box Implementations -- Advanced Lattice Sieving on GPUs, with Tensor Cores -- Masking and Secret-Sharing -- Fast verification of masking schemes in characteristic two -- On the Power of Expansion: More Efficient Constructions in the Random Probing Model -- Leakage-resilience of the Shamir Secret-sharing Scheme against Physicalbit Leakages -- Leakage, Faults and Tampering -- Leakage Resilient Value Comparison With Application to Message Authentication -- The Mother of All Leakages: How to Simulate Noisy Leakages via Bounded Leakage (Almost) for Free -- Message-recovery Laser Fault Injection Attack on the Classic McEliece Cryptosystem -- Multi-Source Non-Malleable Extractors and Applications -- Quantum Constructions and Proofs -- Secure Software Leasing -- Oblivious Transfer is in MiniQCrypt -- Security Analysis of Quantum Lightning -- Classical vs Quantum Random Oracles -- On the Compressed-Oracle Technique, and Post-Quantum Security of Proofs of Sequential Work -- Classical proofs of quantum knowledge -- Multiparty Computation -- Order-C Secure Multiparty Computation for Highly Repetitive Circuits -- The More The Merrier: Reducing the Cost of Large Scale MPC -- Multi-Party Reusable Non-Interactive Secure Computation from LWE -- Unbounded Multi-Party Computation from Learning with Errors -- Generic Compiler for Publicly Verifiable Covert Multi-Party Computation -- Constant-Overhead Unconditionally Secure Multiparty Computation over Binary Fields -- Breaking the Circuit Size Barrier for Secure Computation under Quasi-Polynomial LPN -- Function Secret Sharing for Mixed-Mode and Fixed-Point Secure Computation -- VOLE-PSI: Fast OPRF and Circuit-PSI from Vector-OLE.

The 3-volume-set LNCS 12696 - 12698 constitutes the refereed proceedings of the 40th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Eurocrypt 2021, which was held in Zagreb, Croatia, during October 17-21, 2021. The 78 full papers included in these proceedings were accepted from a total of 400 submissions. They were organized in topical sections as follows: Part I: Best papers; public-key cryptography; isogenies; post-quantum cryptography; lattices; homomorphic encryption; symmetric cryptanalysis; Part II: Symmetric designs; real-world cryptanalysis; implementation issues; masking and secret-sharing; leakage, faults and tampering; quantum constructions and proofs; multiparty computation; Part III: Garbled circuits; indistinguishability obfuscation; non-malleable commitments; zero-knowledge proofs; property-preserving hash functions and ORAM; blockchain; privacy and law enforcement.