This book constitutes the refereed post-conference proceedings of the 4th International Conference on Number-Theoretic Methods in Cryptology, NuTMiC 2024, held in Szczecin, Poland, during June 24–26, 2024.The 9 full papers and 2 invited papers presented in this book were carefully reviewed and selected from 12 submissions. They were organized in topical sections as follows: invited talks; elliptic curves in cryptography; number theory; algebraic structures and public-key cryptography.