This book constitutes the proceedings of the 19th IMA International Conference, IMACC 2023, held in London, UK, during December 12-14, 2023 The 14 full papers included in this volume were carefully reviewed and selected from 36 submissions. This volume presents cutting-edge results in a variety of areas, including coding theory, symmetric cryptography, zeroknowledge protocols, digital signature schemes and extensions, post-quantum cryptography and cryptography in practice.