Public-Key Function-Private Hidden Vector Encryption (And More)
ADVANCES IN CRYPTOLOGY - ASIACRYPT 2019, PT III(2019)
摘要
We construct public-key function-private predicate encryption for the "small superset functionality," recently introduced by Beullens and Wee (PKC 2019). This functionality captures several important classes of predicates:- Point functions. For point function predicates, our construction is equivalent to public-key function-private anonymous identity-based encryption.- Conjunctions. If the predicate computes a conjunction, our construction is a public-key function-private hidden vector encryption scheme. This addresses an open problem posed by Boneh, Raghunathan, and Segev (ASIACRYPT 2013).- d-CNFs and read-once conjunctions of d-disjunctions for constantsize d.Our construction extends the group-based obfuscation schemes of Bishop et al. (CRYPTO 2018), Beullens and Wee (PKC 2019), and Bartusek et al. (EUROCRYPT 2019) to the setting of public-key function-private predicate encryption. We achieve an average-case notion of function privacy, which guarantees that a decryption key skf reveals nothing about f as long as f is drawn from a distribution with sufficient entropy. We formalize this security notion as a generalization of the (enhanced) real-orrandom function privacy definition of Boneh, Raghunathan, and Segev (CRYPTO 2013). Our construction relies on bilinear groups, and we prove security in the generic bilinear group model.
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