Welcome to the resource topic for 2024/1857
Title:
Access-Controlled Inner Product Function-Revealing Encryption
Authors: Ojaswi Acharya, Weiqi Feng, Roman Langrehr, Adam O'Neill
Abstract:We extend the concept of access control for functional encryption, introduced by Abdalla et al. (ASIACRYPT 2020), to function-revealing encryption (Joy and Passelègue, SCN 2018). Here “access control”
means that function evaluation is only possible when a specified access
policy is met. Specifically, we introduce access-controlled inner-product function-revealing encryption (AC-IPFRE) and give two applications.
On the theoretical side, we use AC-IPFRE to show that function-
hiding inner-product functional encryption (FH-IPFE), introduced by
Bishop et al. (ASIACRYPT 2015), is equivalent to IPFRE. To show
this, we in particular generically construct AC-IPFRE from IPFRE for
the “non-zero inner-product” (NZIP) access policy. This result uses an effective version of Lagrange’s Four Square Theorem. One consequence of this result is that lower bounds by Ünal (EUROCRYPT 2020) suggest that, as for FH-IPFE, bilinear pairings will be needed to build IPFRE.
On the practical side, we build an outsourced approximate nearest-
neighbor (ANN) search protocol and mitigate its leakage via AC-IPFRE.
For this, we construct a practical AC-IPFRE scheme in the generic
bilinear group model for a specific access policy for ANN search. To this end, we show that techniques of Wee (TCC 2020) implicitly give the most practical FH-IPFE scheme to date. We implement the resulting
outsourced ANN search protocol and report on its performance.
Of independent interest, we show AC-IPFRE for NZIP implies
attribute-hiding small-universe AC-IPFRE for arbitrary access policies.
Previous work on access control for FE did not achieve attribute hiding.
Overall, our results demonstrate that AC-IPFRE is of both theoretical
and practical interest and set the stage for future work in the area.
ePrint: https://eprint.iacr.org/2024/1857
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