Cryptology ePrint Archive: Report 2018/696

Unbounded Inner Product Functional Encryption from Bilinear Maps

Junichi Tomida and Katsuyuki Takashima

Abstract: Inner product functional encryption (IPFE), introduced by Abdalla et al. (PKC2015), is a kind of functional encryption supporting only inner product functionality. All previous IPFE schemes are bounded schemes, meaning that the vector length that can be handled in the scheme is fixed in the setup phase. In this paper, we propose the first unbounded IPFE schemes, in which we do not have to fix the lengths of vectors in the setup phase and can handle (a priori) unbounded polynomial lengths of vectors. Our first scheme is private-key based and fully function hiding. That is, secret keys hide the information of the associated function. Our second scheme is public-key based and provides adaptive security in the indistinguishability based security definition. Both our schemes are based on SXDH, which is a well-studied standard assumption, and secure in the standard model. Furthermore, our schemes are quite efficient, incurring an efficiency loss by only a small constant factor from previous bounded function hiding schemes.

Category / Keywords: public-key cryptography / functional encryption, inner product, function hiding, unbounded, bilinear maps

Original Publication (with major differences): IACR-ASIACRYPT-2018

Date: received 18 Jul 2018, last revised 9 Sep 2018

Contact author: tomida junichi at lab ntt co jp

Available format(s): PDF | BibTeX Citation

Note: fixing a citation error

Version: 20180910:042010 (All versions of this report)

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