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This paper presents PrPl, a decentralized infrastructure that lets users participate in online social networking without loss of data ownership. PrPl, short for private-public, has a person-centric architecture--each individual uses a Personal-Cloud Butler service that provides a safe haven for one's personal digital assets and supports sharing with fine-grain access control. A user can choose to run the Butler on a home server, or use a paid or ad-supported vendor of his choice. Each Butler provides a federation of data storage; it keeps a semantic index to data that can reside, possibly encrypted, in other storage services. It uses the standard, decentralized OpenID management system, so users can use their established personas in accessing the data.
Seong et al. (Tue,) studied this question.