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.