As the use of personal information in social network sites seems manifold, including the representation of an individual's digital persona (or social role) and identification, so does the abuse or misuse of the information. The issue of privacy is critically important in this context. In this paper we present a novel framework for enabling user-controlled sharing of sensitive personal information for better privacy protection in current online social networks. Specifically, the framework called U-Control is proposed to facilitate digital persona and privacy management (DPPM) in a user-centric way that it can satisfy diverse privacy requirements and specification, and social network environments. We discuss the design of a security system based on the proposed framework. Finally we discuss a proof-of-concept implementation, along with performance evaluation.