Private Discovery of Common Social Contacts

The increasing use of computing devices for social interactions propels the proliferation of online social applications, yet, it prompts a number of privacy concerns. One common problem occurs when two unfamiliar users, in the process of establishing social relationships, want to assess their social proximity by discovering mutual contacts. In this paper, we introduce Private Contact Discovery, a novel cryptographic primitive that lets two users, on input their respective contact lists, learn their common contacts (if any), and nothing else. We present an efficient and provably secure construction, that (i) prevents arbitrary list manipulation by means of contact certification, and (ii) guarantees user authentication and revocability. Following a rigorous cryptographic treatment of the problem, we define the privacy-protecting contact-hiding property and prove it for our solution, under the RSA assumption in the Random Oracle Model (ROM). We also show that other related cryptographi...

• Type: Journal
• Year: 2011
• Where: ACNS
• Authors: Emiliano De Cristofaro, Mark Manulis, Bertram Poettering
• Keywords: ACNS 2011, Cryptology, Random Oracle Model, RSA Assumption, Secret Handshakes