Cryptology ePrint Archive: Report 2021/1381

Multi-Authority ABE, Revisited

Miguel Ambrona and Romain Gay

Abstract: Attribute-Based Encryption (ABE) is a cryptographic primitive which supports fine-grained access control on encrypted data, making it an appealing building block for many applications. Multi-Authority Attribute-Based Encryption (MA-ABE) is a generalization of ABE where the central authority is distributed across several independent parties.

We provide the first MA-ABE scheme from prime-order pairings where no trusted setup is needed and where the attribute universe of each authority is unbounded. Our constructions rely on a common modular blueprint that uses an Identity-Based Functional Encryption scheme for inner products (ID-IPFE) as an underlying primitive. Our presentation leads to simple proofs of security and brings new insight into the algebraic design choices that seem common to existing schemes. In particular, the well-known MA-ABE construction by Lewko and Waters (EUROCRYPT 2011) can be seen as a specific instantiation of our modular construction.

Our schemes enjoy all of their advantageous features, and the improvements mentioned. Furthermore, different instantiations of the core ID-IPFE primitive lead to various security/efficiency trade-offs: we propose an adaptively secure construction proven in the generic group model and a selectively secure one that relies on SXDH. As in previous work, we rely on a hash function (to generate matching randomness for the same user across different authorities while preserving collusion resistance) that is modeled as a random oracle.

Category / Keywords: public-key cryptography / attribute-based encryption, pairing-based crypto, multi-authority, generic group model, inner products, functional encryption

Date: received 12 Oct 2021, last revised 13 Oct 2021

Contact author: romain rgay at gmail com, mac ambrona at gmail com

Available format(s): PDF | BibTeX Citation

Version: 20211015:082227 (All versions of this report)

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