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Erschienen in:
2015 | OriginalPaper | Buchkapitel
Separations in Circular Security for Arbitrary Length Key Cycles
verfasst von : Venkata Koppula, Kim Ramchen, Brent Waters
Erschienen in: Theory of Cryptography
Verlag: Springer Berlin Heidelberg
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While standard notions of security suffice to protect any message supplied by an adversary, in some situations stronger notions of security are required. One such notion is
n-circular
security, where ciphertexts
Enc(pk
1
, sk
2
), Enc(pk
2
, sk
3
), . . . , Enc(pk
n
, sk
1
)
should be indistinguishable from encryptions of zero.
In this work we prove the following results for
n
-circular security, based upon recent candidate constructions of indistinguishability obfuscation [18,16] and one way functions:
– For any
n
there exists an encryption scheme that is
IND-CPA
secure but not
n
-circular secure.
– There exists a bit encryption scheme that is
IND-CPA
secure, but not 1-circular secure.
– If there exists an encryption system where an attacker can distinguish a key encryption cycle from an encryption of zeroes, then in a transformed cryptosystem there exists an attacker which recovers secret keys from the encryption cycles.
The last result is generic and applies to any such cryptosystem.