The four-volume proceedings LNCS 13090, 13091, 13092, and 13093 constitutes the proceedings of the 27th International Conference on the Theory and Application of Cryptology and Information Security, ASIACRYPT 2021, which was held during December 6-10, 2021.

NTRU Fatigue: How Stretched is Overstretched?.- Faster Dual Lattice Attacks for Solving LWE -- with applications to CRYSTALS.- Lattice sieving via quantum random walks.- A Systematic Approach and Analysis of Key Mismatch Attacks on Lattice-Based NIST Candidate KEMs.- Gladius: LWR based efficient hybrid public key encryption with distributed decryption.- Lattice-Based Group Encryption with Full Dynamicity and Message Filtering Policy.- A New Variant of Unbalanced Oil and Vinegar Using Quotient Ring: QR-UOV.- Shorter Lattice-Based Group Signatures via ``Almost Free'' Encryption and Other Optimizations.- Séta: Supersingular Encryption from Torsion Attacks.- SHealS and HealS: isogeny-based PKEs from a key validation method for SIDH.- Adaptive Security via Deletion in Attribute-Based Encryption: Solutions from Search Assumptions in Bilinear Groups.- Public Key Encryption with Flexible Pattern Matching.- Bounded Collusion ABE for TMs from IBE.- Digital Signatures with Memory-Tight Security in the Multi-Challenge Setting.- (Compact) Adaptively Secure FE for Attribute-Weighted Sums from k-Lin.- Boosting the Security of Blind Signature Schemes.- PrORAM: Fast O(log n) Authenticated Shares ZK ORAM.- Compressed Sigma-Protocols for Bilinear Group Arithmetic Circuits and Application to Logarithmic Transparent Threshold Signatures.- Promise $\Sigma$-protocol: How to Construct Efficient Threshold ECDSA from Encryptions Based on Class Groups.- The One-More Discrete Logarithm Assumption in the Generic Group Model.- Verifiably-Extractable OWFs and Their Applications to Subversion Zero-Knowledge.- Chain Reductions for Multi-Signatures and the HBMS Scheme.- Symmetric Key Exchange with Full Forward Security and Robust Synchronization.- Security Analysis of CPace.- Modular Design of Role-Symmetric Authenticated Key Exchange Protocols.

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