Paper 2019/233

Unbounded Dynamic Predicate Compositions in Attribute-Based Encryption

Nuttapong Attrapadung

Abstract

We present several transformations that combine a set of attribute-based encryption (ABE) schemes for simpler predicates into a new ABE scheme for more expressive composed predicates. Previous proposals for predicate compositions of this kind, the most recent one being that of Ambrona et.al. at Crypto'17, can be considered static (or partially dynamic), meaning that the policy (or its structure) that specifies a composition must be fixed at the setup. Contrastingly, our transformations are dynamic and unbounded: they allow a user to specify an arbitrary and unbounded-size composition policy right into his/her own key or ciphertext. We propose transformations for three classes of composition policies, namely, the classes of any monotone span programs, any branching programs, and any deterministic finite automata. These generalized policies are defined over arbitrary predicates, hence admitting modular compositions. One application from modularity is a new kind of ABE for which policies can be ``nested'' over ciphertext and key policies. As another application, we achieve the first fully secure completely unbounded key-policy ABE for non-monotone span programs, in a modular and clean manner, under the q-ratio assumption. Our transformations work inside a generic framework for ABE called symbolic pair encoding, proposed by Agrawal and Chase at Eurocrypt'17. At the core of our transformations, we observe and exploit an unbounded nature of the symbolic property so as to achieve unbounded-size policy compositions.

Metadata
Available format(s)
PDF
Publication info
A major revision of an IACR publication in EUROCRYPT 2019
Keywords
attribute-based encryptionpredicate encryptionnested policyautomatapair encodingsymbolic securitydynamic compositionfull securitynon-monotone span programs
Contact author(s)
n attrapadung @ aist go jp
History
2019-02-28: received
Short URL
https://ia.cr/2019/233
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2019/233,
      author = {Nuttapong Attrapadung},
      title = {Unbounded Dynamic Predicate Compositions in Attribute-Based Encryption},
      howpublished = {Cryptology {ePrint} Archive, Paper 2019/233},
      year = {2019},
      url = {https://eprint.iacr.org/2019/233}
}
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