Authenticating with Attributes in Online Social Networks

In online social networks (OSN), users´ capabilities of accessing a resource depend on attributes they owning. Considering of privacy, authentication with attributes require the signer don´t leak more information than the predicate over attributes involving. There´re some works of attribute-based signatures (ABS) to satisfy this requirement, where users sign messages with their attributes issued from an attribute authority, and a signature attests not to the identity of the individual who signed a message, but a claim regarding the attributes the underlying signer possesses. However, none of existing works achieve expressive predicate or security under standard Diffie-Hellman assumption at the same time. In this paper, we propose an ABS scheme using attribute tree, which expresses any predicate consisting of AND, OR, Threshold gates, under standard Diffie-Hellman problem. Users cannot forge signatures with attributes they do not possess, and the signature assures that only a user with appropriate attributes satisfying the predicate endorse the message, resulting in unforgeability. On the other hand, a legitimate signer remains anonymous without the fear of revocation and is indistinguishable among all the users whose attributes satisfying the predicate specified in the signature, that is, attribute-signer privacy. Our scheme is suitable for authentication in OSN.