The four-volume set LNCS 16268-16271 constitutes the refereed proceedings of the 23rd International Conference on Theory of Cryptography, TCC 2025, held in Aarhus, Denmark, during December 1-5, 2025.The total of 70 full papers presented in the proceedings was carefully reviewed and selected from 242 submissions. They were organized in topical sections as follows:

Part I: Secure Computation; Homomorphic Primitives; Proofs;

Part II: Foundations; Obfuscation and Functional Encryption; Secret Sharing;

Part III: Quantum Cryptography; Signatures and Intractability Assumptions;

Part IV: Proofs; Young Researcher Award and Outstanding Paper Awards; Differential Privacy; Times Cryptography and Verifiable Random Function; Secure Computation.