In this work we describe the PriSM framework for decentralized deployment of a federation of autonomous social networks (ASN). The individual ASNs are centrally managed by organizations according to their institutional needs, while cross-ASN interactions are facilitated subject to security and confidentiality requirements specified by administrators and users of the ASNs. Such decentralized deployment, possibly either on private or public clouds, provides control and ownership of information/flow to individual organizations. Lack of such complete control (if third party online social networking services were to be used) has so far been a great barrier in taking full advantage of the novel communication mechanisms at workplace that have however become commonplace for personal usage with the advent of Web 2.0 platforms and online social networks. PriSM provides a practical solution for organizations to harness the advantages of online social networking both in intra/inter-organizational settings without sacrificing autonomy, security and confidentiality needs.
Interactive hashing, introduced by Naor, Ostrovsky, Venkatesan, and Yung (J. Cryptol. 11(2):87–108, 1998 ), plays an important role in many cryptographic protocols. In particular, interactive hashing is a major component in all known constructions of statistically hiding commitment schemes and of statistical zero-knowledge arguments based on general one-way permutations/functions. Interactive hashing with respect to a one-way function f is a two-party protocol that enables a sender who knows y = f ( x ) to transfer a random hash z = h ( y ) to a receiver such that the sender is committed to y : the sender cannot come up with x and x ′ such that f ( x )≠f ( x ′), but h ( f ( x ))= h ( f ( x ′))= z . Specifically, if f is a permutation and h is a two-to-one hash function, then the receiver does not learn which of the two preimages { y , y ′}= h −1 ( z ) is the one the sender can invert with respect to f . This paper reexamines the notion of interactive hashing, and proves the security of a variant of the Naor et al. protocol, which yields a more versatile interactive hashing theorem. When applying our new proof to (an equivalent variant of) the Naor et al. protocol, we get an alternative proof for this protocol that seems simpler and more intuitive than the original one, and achieves better parameters (in terms of how security preserving the reduction is).
In this paper, we introduce the concept of additive zero knowledge. Essentially, an additive proof can be considered as a proof system involving many provers and one verifier such that the statements of all the provers are proved simultaneously. Our model of additive proofs is presented using constructions of blind group identification, aggregate signatures and chained signatures. The security of our protocols relies on the difficulty of the underlying Diffie-Hellman problem in bilinear maps. As applications, we present a novel method to prevent spam.