In this dissertation, we present peer-to-peer file sharing application designs and implementations that run on top of the Named Data Networking (NDN) architecture. NDN provides a data-centric communication model directly at the network layer, as well as data-centric security primitives, making security a property of the data that stays with it at rest and in transit across the network. Our experimental results show that NDN’s named and secured data, adaptive forwarding, and caching provide a solid foundation for peer-to-peer applications both in infrastructure-based and mobile ad-hoc networks, achieving lower data dissemination delays and overheads compared to TCP/IP-based solutions.