April 2016
Beginner to intermediate
463 pages
18h 53m
English
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Cryptography for Big Data Security
251
decrypt data for which neither of their keys individually satisfies the access formula. This is typ-
ically the hardest feature of ABE to achieve and requires stronger cryptographic assumptions.
10.3.2.3 Survey
10.3.2.3.1 A first attempt
As a first attempt to constructing ABE, we can do the following. Let each cryptographic key
correspond to an attribute, so k
A
is given to all users with attribute A. Now, to encrypt a piece of
data so that only those possessing attributes A and B can decrypt, we can encrypt the data first
under k
A
and then under k
B
, resulting in c = Enc
k
B
(Enc
k
A
(x)). Clearly, both keys are needed
to