Typical Web 2.0 applications are built on abstractions, allowing developers to rapidly and securely develop new features. For decentralised applications, these abstractions are often poor or non-existent.By proposing a set of abstract but generic building blocks for the development of peer-to-peer (decentralised), private online social networks, we aim to ease the development of user-facing applications. Additionally, an abstract programming system decouples the application from the data model, allowing to alter the front-end independently from the back-end.The proposed proof-of-concept protocol is based on existing cryptographic building blocks, and its viability is assessed in terms of performance.