The two-volume proceedings constitutes the refereed proceedings of the 24th International Conference on Progress in Cryptology, INDOCRYPT 2023, Goa, India, in December 2023. The 26 full papers were carefully reviewed and selected from 74 submissions. They are organized in topical sections as follows: Part I: Symmetric-key cryptography, Hash functions, Authenticated Encryption Modes; Elliptic curves, Zero-knowledge proof, Signatures; Attacks. Part II: Secure computation, Algorithm hardness, Privacy; Post-quantum cryptography. .