The two-volume proceedings set LNCS 12710 and 12711 constitutes the proceedings of the 24th IACR International Conference on Practice and Theory of Public Key Cryptography, PKC 2021, which was held online during May 10-13, 2021.

Cryptographic Primitives and Schemes.- More Efficient Digital Signatures with Tight Multi-User Security.- Multiparty Cardinality Testing for Threshold Private Set Intersection.- Verifiable Random Functions with Optimal Tightness.- A Geometric Approach to Homomorphic Secret Sharing.- Generic Negation of Pair Encodings.- On Selective-Opening Security of Deterministic Primitives.- Revisiting (R)CCA Security and Replay Protection.- Cryptographic Protocols.- Single-to-Multi-Theorem Transformations for Non-Interactive Statistical Zero-Knowledge.- On the CCA Compatibility of Public-Key Infrastructure.- Round-optimal Verifiable Oblivious Pseudorandom Functions from Ideal Lattices.- BETA: Biometric-Enabled Threshold Authentication.- Masked Triples: Amortizing Multiplication Triples across Conditionals.- Multi-Party Threshold Private Set Intersection with Sublinear Communication.- On the (In)Security of the Di e-Hellman Oblivious PRF with Multiplicative Blinding.- An Efficient and Generic Construction for Signal's Handshake (X3DH): Post-Quantum, State Leakage Secure, and Deniable.- Cryptographic Pseudorandom Generators Can Make Cryptosystems Problematic.- Publicly Verifiable Zero Knowledge from (Collapsing) Blockchains.- Two-server Distributed ORAM with Sublinear Computation and Constant Rounds.- Flexible and Efficient Verifiable Computation on Encrypted Data.- Transferable E-cash: A Cleaner Model and the First Practical Instantiation.- Private Set Operations from Oblivious Switching.- On Publicly-Accountable Zero-Knowledge and Small Shuffle Arguments.- Beyond Security and E ciency: On-Demand Ratcheting with Security Awareness.- Group Encryption: Full Dynamicity, Message Filtering and Code-Based Instantiation.- Steel: Composable Hardware-based Stateful and Randomised Functional Encryption.- Attacks and Cryptanalysis.- Adventures in Crypto Dark Matter: Attacks and Fixes for Weak Pseudorandom Functions.