IACR News item: 27 September 2013
Marcin Nagy, Emiliano De Cristofaro, Alexandra Dmitrienko, N. Asokan, Ahmad-Reza Sadeghi
ePrint ReportThis paper introduces the Common Friends service, a framework for finding common friends which protects privacy of non-mutual friends and guarantees authenticity of friendships. First, we present a generic construction that reduces to secure computation of set intersection, while ensuring authenticity of announced friends via bearer capabilities. Then, we propose an efficient instantiation, based on Bloom filters, that only incurs a constant number of public-key operations and appreciably low communication overhead. Our software is designed so that developers can easily integrate Common Friends into their applications, e.g., to enforce access control based on users\' social proximity in a privacy-preserving manner. Finally, we showcase our techniques in the context of an existing application for sharing (tethered) Internet access, whereby users decide to share access depending on the existence of common friends. A comprehensive experimental evaluation attests to the practicality of proposed techniques.
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