Blind key-generation attribute-based encryption for general predicates

Abstract

Attribute-based encryption (ABE) is a form of public-key encryption that allows fine-grained access control on encrypted data. Blind key-generation (BKG) attribute-based encryption (Rial, Designs, Codes and Cryptography 2016) is a variant in which the master authority issues secret keys without learning any information about the attributes associated to them. This extra functionality makes it an appealing building block for several applications. In this work, we extend the generic framework of ABE based on pair encodings (Attrapadung, Eurocrypt 2014) to support blind key-generation. In particular, we define two new notions of pair encodings that we coin BKG-compatible and algebraic pair encoding. We show that every encoding satisfies the former without loss of generality, whereas the latter is satisfied by all existing pair encodings from the literature. We then show how to enhance any ABE based on a BKG-compatible pair encoding to achieve honest-but-curious blind key-generation. In the case of algebraic encodings, our protocol admits a very efficient version, secure against malicious parties. The main advantage of our work is generality. Our protocol is designed over the recent and most advanced modular frameworks of ABE that can handle a rich variety of predicates.