2014 | OriginalPaper | Buchkapitel
Fully Key-Homomorphic Encryption, Arithmetic Circuit ABE and Compact Garbled Circuits
verfasst von : Dan Boneh, Craig Gentry, Sergey Gorbunov, Shai Halevi, Valeria Nikolaenko, Gil Segev, Vinod Vaikuntanathan, Dhinakaran Vinayagamurthy
Erschienen in: Advances in Cryptology – EUROCRYPT 2014
Verlag: Springer Berlin Heidelberg
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We construct the first (key-policy) attribute-based encryption (ABE) system with short secret keys: the size of keys in our system depends only on the depth of the policy circuit, not its size. Our constructions extend naturally to arithmetic circuits with arbitrary fan-in gates thereby further reducing the circuit depth. Building on this ABE system we obtain the first reusable circuit garbling scheme that produces garbled circuits whose size is the same as the original circuit
plus
an additive
poly
(
λ
,
d
) bits, where
λ
is the security parameter and
d
is the circuit depth. All previous constructions incurred a
multiplicative
poly
(
λ
) blowup.
We construct our ABE using a new mechanism we call
fully key-homomorphic encryption
, a public-key system that lets anyone translate a ciphertext encrypted under a public-key x into a ciphertext encrypted under the public-key (
f
(
x
),
f
) of the same plaintext, for any efficiently computable
f
. We show that this mechanism gives an ABE with short keys. Security of our construction relies on the subexponential hardness of the learning with errors problem.
We also present a second (key-policy) ABE, using multilinear maps, with short ciphertexts: an encryption to an attribute vector x is the size of x plus
poly
(
λ
,
d
) additional bits. This gives a reusable circuit garbling scheme where the garbled input is short.