Searchable Encryption -- Public Key Based Searchable Encryption with Fine-Grained Sender Permission Control -- Improved Security Model for Public-key Authenticated Encryption with Keyword Search -- Public Key Encryption with Fuzzy Matching -- Partitioned Searchable Encryption -- Key Exchange & Zero Knowledge Proof -- Key Exposure Resistant Group Key Agreement Protocol -- NIKE from Affine Determinant Programs -- OrBit: OR-Proof Identity-Based Identification with Tight Security for (as low as) 1-bit Loss -- Card-based Zero-knowledge Proof Protocols for Graph Problems and Their Computational Model -- Post Quantum Cryptography -- Recovery Attack on Bob's Reused Randomness in CRYSTALS-KYBER and SABERA Lattice Reduction Algorithm Based on Sublattice BKZ -- On the (M)iNTRU assumption in the integer case -- Functional Encryption -- Verifiable Functional Encryption using Intel SGX -- Fully Secure Unbounded Zero Inner Product Encryption with Short Ciphertexts and Keys -- Inner-Product Functional Encryption from Random Linear Codes: Trial and Challenges -- Digital Signature -- A CCA-full-anonymous Group Signature with Verifiable Controllable Linkability in the Standard Model -- Cryptanalysis of LRainbow: The Lifted Rainbow Signature Scheme -- Identification Scheme and Forward-Secure Signature in Identity-Based Setting from Isogenies -- Linearly Homomorphic Signatures with Designated Combiner -- Efficient Attribute-Based Signature for monotone predicates -- Practical Security Protocols -- Spatial Steganalysis Based on Gradient-Based Neural Architecture Search -- Turn-Based Communication Channels -- .

This book constitutes the refereed proceedings of the 15th International Conference on Provable Security, ProvSec 2021, held in Guangzhou, China, in November 2021. The 21 full papers presented were carefully reviewed and selected from 67 submissions. The papers focus on provable security as an essential tool for analyzing security of modern cryptographic primitives. They are divided in the following topical sections: Searchable Encryption, Key Exchange & Zero Knowledge Proof, Post Quantum Cryptography, Functional Encryption, Digital Signature, and Practical Security Protocols.