---
res:
  bibo_abstract:
  - 'A pseudorandom function (PRF) is a keyed function F : K × X → Y where, for a
    random key k ∈ K, the function F(k, ·) is indistinguishable from a uniformly random
    function, given black-box access. A key-homomorphic PRF has the additional feature
    that for any keys k, k'' and any input x, we have F(k+k'', x) = F(k, x)⊕F(k'',
    x) for some group operations +,⊕ on K and Y, respectively. A constrained PRF for
    a family of setsS ⊆ P(X) has the property that, given any key k and set S ∈ S,
    one can efficiently compute a “constrained” key kS that enables evaluation of
    F(k, x) on all inputs x ∈ S, while the values F(k, x) for x /∈ S remain pseudorandom
    even given kS. In this paper we construct PRFs that are simultaneously constrained
    and key homomorphic, where the homomorphic property holds even for constrained
    keys. We first show that the multilinear map-based bit-fixing and circuit-constrained
    PRFs of Boneh and Waters (Asiacrypt 2013) can be modified to also be keyhomomorphic.
    We then show that the LWE-based key-homomorphic PRFs of Banerjee and Peikert (Crypto
    2014) are essentially already prefix-constrained PRFs, using a (non-obvious) definition
    of constrained keys and associated group operation. Moreover, the constrained
    keys themselves are pseudorandom, and the constraining and evaluation functions
    can all be computed in low depth. As an application of key-homomorphic constrained
    PRFs,we construct a proxy re-encryption schemewith fine-grained access control.
    This scheme allows storing encrypted data on an untrusted server, where each file
    can be encrypted relative to some attributes, so that only parties whose constrained
    keys match the attributes can decrypt. Moreover, the server can re-key (arbitrary
    subsets of) the ciphertexts without learning anything about the plaintexts, thus
    permitting efficient and finegrained revocation.@eng'
  bibo_authorlist:
  - foaf_Person:
      foaf_givenName: Abishek
      foaf_name: Banerjee, Abishek
      foaf_surname: Banerjee
  - foaf_Person:
      foaf_givenName: Georg
      foaf_name: Fuchsbauer, Georg
      foaf_surname: Fuchsbauer
      foaf_workInfoHomepage: http://www.librecat.org/personId=46B4C3EE-F248-11E8-B48F-1D18A9856A87
  - foaf_Person:
      foaf_givenName: Chris
      foaf_name: Peikert, Chris
      foaf_surname: Peikert
  - foaf_Person:
      foaf_givenName: Krzysztof Z
      foaf_name: Pietrzak, Krzysztof Z
      foaf_surname: Pietrzak
      foaf_workInfoHomepage: http://www.librecat.org/personId=3E04A7AA-F248-11E8-B48F-1D18A9856A87
    orcid: 0000-0002-9139-1654
  - foaf_Person:
      foaf_givenName: Sophie
      foaf_name: Stevens, Sophie
      foaf_surname: Stevens
  bibo_doi: 10.1007/978-3-662-46497-7_2
  bibo_volume: 9015
  dct_date: 2015^xs_gYear
  dct_isPartOf:
  - http://id.crossref.org/issn/978-3-662-46496-0
  dct_language: eng
  dct_publisher: Springer Nature@
  dct_title: Key-homomorphic constrained pseudorandom functions@
...