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Erschienen in:
2014 | OriginalPaper | Buchkapitel
Obfuscation ⇒ (IND-CPA Security Circular Security)
verfasst von : Antonio Marcedone, Claudio Orlandi
Erschienen in: Security and Cryptography for Networks
Verlag: Springer International Publishing
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Circular security
is an important notion for public-key encryption schemes and is needed by several cryptographic protocols. In circular security the adversary is given an extra “hint” consisting of a
cycle
of encryption of secret keys i.e.,
$\left(E_{pk_1}(sk_2),\ldots, E_{pk_n}(sk_1)\right)$
. A natural question is whether every IND-CPA encryption scheme is also circular secure. It is trivial to see that this is not the case when
n
= 1. In 2010 a separation for
n
= 2 was shown by [ABBC10,GH10] under standard assumptions in bilinear groups.
In this paper we finally settle the question showing that for every
n
there exists an IND-CPA secure scheme which is not
n
-circular secure.
Our result relies on the recent progress in cryptographic obfuscation.