§16§This book constitutes the refereed proceedings of the 20th International Conference on Cryptology and Network Security, CANS 2021, which was held during December 13-15, 2021. The conference was originally planned to take place in Vienna, Austria, and changed to an online event due to the COVID-19 pandemic.§The 25 full and 3 short papers presented in these proceedings were carefully reviewed and selected from 85 submissions. They were organized in topical sections as follows: Encryption; signatures; cryptographic schemes and protocols; attacks and counter-measures; and attestation and verification.§ §04§Encryption.- Cross-Domain Attribute-Based Access Control Encryption.- Grain-128AEADv2: Strengthening the Initialization Against Key Reconstruction.- Partition Oracles from Weak Key Forgeries.- Practical Privacy-Preserving Face Identification based on FunctionHiding Functional Encryption.- The Matrix Reloaded: Multiplication Strategies in FrodoKEM.- Signatures.- BlindOR: An Effcient Lattice-Based Blind Signature Scheme from OR-Proofs.- Effcient Threshold-Optimal ECDSA.- GMMT: A Revocable Group Merkle Multi-Tree Signature Scheme.- Issuer-Hiding Attribute-Based Credentials.- Report and Trace Ring Signatures.- Selectively Linkable Group Signatures - Stronger Security and Preserved Verifiability.- Cryptographic Schemes and Protocols.- FO-like Combiners and Hybrid Post-Quantum Cryptography.- Linear-time oblivious permutations for SPDZ.- On the Higher-bit Version of Approximate Inhomogeneous Short Integer Solution Problem.- Practical Continuously Non-Malleable Randomness Encoders in the §04§Random Oracle Model.- Attacks and Counter-Measures.- Countermeasures against Backdoor Attacks towards Malware Detectors.- Free By Design: On the Feasibility Of Free-Riding Attacks Against Zero-Rated Services.- Function-private Conditional Disclosure of Secrets and Multi-evaluation Threshold Distributed Point Functions.- How Distance-bounding can Detect Internet Traffc Hijacking.- SoK: Secure Memory Allocation.- Toward Learning Robust Detectors from Imbalanced Datasets Leveraging Weighted Adversarial Training.- Towards Quantum Large-Scale Password Guessing on Real-World Distributions.- Attestation and Verification.- Anonymous Transactions with Revocation and Auditing in Hyperledger Fabric.- Attestation Waves: Platform Trust via Remote Power Analysis.- How (not) to Achieve both Coercion Resistance and Cast as Intended Verifiability in Remote eVoting.- Subversion-Resistant Quasi-Adaptive NIZK and Applications to Modular zk-SNARKs.- THC: Practical and Cost-Effective Verification of De §04§legated Computation.- Tiramisu: Black-Box Simulation Extractable NIZKs in the Updatable CRS Model.
