  Online Social Networks (OSNs) have become one of the most important
activities on the Internet, such as Facebook and Google+. However, security and
privacy have become major concerns in existing C/S based OSNs. In this paper,
we propose a novel scheme called a Privacy-preserving Community-based P2P OSNs
Using Broadcast Encryption Supporting Recommendation Mechanism (PCBE) that
supports cross-platform availability in stringent privacy requirements. For the
first time, we introduce recommendation mechanism into a privacy-preserving P2P
based OSNs, in which we firstly employ the Open Directory Project to generate
user interest model. We firstly introduce broadcast encryption into P2P
community-based social networks together with reputation mechanism to decrease
the system overhead. We formulate the security requirements and design goals
for privacy- preserving P2P based OSNs supporting recommendation mechanism. The
RESTful web-services help to ensure cross-platform availability and
transmission security. As a result, thorough security analysis and performance
evaluation on experiments demonstrate that the PCBE scheme indeed accords with
our proposed design goals.
