The need for controlled (privacy-preserving) sharing of sensitive information occurs in many different and realistic everyday scenarios, ranging from national security to social networking. A typical setting involves two parties: one seeks information from the other without revealing the interest while the latter is either willing, or compelled, to share only the requested information. This poses two challenges: (1) how to enable this type of sharing such that parties learn no information

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... what they are entitled to, and (2) how to do so efficiently, in real-world practical terms. This paper explores the notion of Privacy-Preserving Sharing of Sensitive Information (PPSSI), and provides two concrete and efficient instantiations, modeled in the context of simple database querying. Proposed techniques function as a privacy shield to protect parties from disclosing more than the required minimum of their respective sensitive information. PPSSI deployment prompts several challenges, that are addressed in this paper. Extensive experimental results attest to the practicality of attained privacy features and show that they incur quite low overhead (about 10% slower than standard MySQL).