---
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
- 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_language: eng
dct_publisher: Springer@
dct_title: Key-homomorphic constrained pseudorandom functions@
...