This book constitutes the proceedings of the 24rd International Conference on Information Security, ISC 2021, held virtually, in November 2021.The 21 full papers presented in this volume were carefully reviewed and selected from 87 submissions. web and OS security; network security; and machine learning for security.

Cryptology.- Integer LWE with Non-Subgaussian Error and Related Attacks.- Layering Quantum-Resistance into Classical Digital Signature Algorithms.- Cryptanalysis of RSA Variants with Primes Sharing Most Significant Bits.- Cryptanalysis of Two White-Box Implementations of the SM4 Block Cipher.- A Non-Interactive Multi-User Protocol for Private Authorised Query Processing on Genomic Data.- Bigdata-facilitated Two-party Authenticated Key Exchange for IoT.- Randomized Component Based Secure Secret Reconstruction in Insecure Networks.- Transparency order of (n,m)-functions — its further characterization and applications.- Web and OS security.- Browserprint: An Analysis of the Impact of Browser Features on Fingerprintability and Web Privacy.- TridentShell: A Covert and Scalable Backdoor Injection.- Andromeda: Enabling Secure Enclaves For The Android Ecosystem.- Network security.- FEX – A feature extractor for real-time IDS.- Identifying Malicious DNS Tunnel Tools from DoH Traffic Using Hierarchical Machine Learning Classification.- Detection of malware, attacks and vulnerabilities.- Hybroid: Toward Android Malware Detection and Categorization with Program Code and Network Traffic.- A Novel Behavioural Screenlogger Detection System.- DEVA: Decentralized, Verifiable Secure Aggregation for Privacy-Preserving Learning.- DVul-WLG: Graph Embedding Network Based on Code Similarity for Cross-architecture Firmware Vulnerability Detection.- Machine learning for security.- Detect and Remove Watermark in Deep Neural Networks via Generative Adversarial Networks.- Targeted Universal Adversarial Perturbations for Automatic Speech Recognition.- Voxstructor: Voice Reconstruction from Voiceprint.- Word-Map: Using Community Detection Algorithm to Detect AGDs.