Searchable Encryption Revisited: Consistency Properties, Relation to Anonymous IBE, and Extensions
We identify and fill some gaps with regard to consistency (the extent to which false positives are produced) for public-key encryption with keyword search (PEKS). We define computational and statistical relaxations of the existing notion of perfect consistency, show that the scheme of Boneh et al. in Eurocrypt 2004 is computationally consistent, and provide a new scheme that is statistically consistent. We also provide a transform of an anonymous IBE scheme to a secure PEKS scheme that, unlike the previous one, guarantees consistency. Finally, we suggest three extensions of the basic notions considered here, namely anonymous HIBE, public-key encryption with temporary keyword search, and identity-based encryption with keyword search.
Foundations of Group Signatures: The Case of Dynamic Groups
A first step toward establishing foundations for group signatures was taken by Bellare, Micciancio and Warinschi (Eurocrypt 2003) with a treatment of the case where the group is static. However the bulk of existing practical schemes and applications are for dynamic groups, and these involve important new elements and security issues. This paper treats this case, providing foundations for dynamic group signatures, in the form of a model, strong formal definitions of security, and a construction proven secure under general assumptions. We believe this is an important and useful step because it helps bridge the gap between Bellare Micciancio and Warinschi and the previous practical work, and delivers a basis on which existing practical schemes may in future be evaluated or proven secure.