The five-volume set LNCS 15674-15678 constitutes the refereed proceedings of the 28th IACR International Conference on Practice and Theory of Public Key Cryptography, PKC 2025, held in Røros, Norway, during May 12-15, 2025. The 60 papers included in these proceedings were carefully reviewed and selected from 199 submissions. They are grouped into these topical sections: MPC and friends; advanced PKE; security of post-quantum signatures; proofs and arguments; multi-signatures; protocols; foundations of lattices and LPN; threshold signatures; isogenies and group actions; secure computation; security against real-world attacks; batch arguments and decentralized encryption; and cryptography for blockchains.