### Abstract

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.

Original language | English |
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Title of host publication | Theory of Cryptography |

Subtitle of host publication | 12th Theory of Cryptography Conference, TCC 2015 Warsaw, Poland, March 23-25, 2015 Proceedings, Part II |

Editors | Yevgeniy Dodis, Jesper Buus Nielsen |

Place of Publication | Berlin Germany |

Publisher | Springer |

Pages | 378-400 |

Number of pages | 23 |

ISBN (Electronic) | 9783662464960 |

ISBN (Print) | 9783662464977 |

DOIs | |

Publication status | Published - 2015 |

Externally published | Yes |

Event | Theory of Cryptography Conference 2015 - Warsaw, Poland Duration: 23 Mar 2015 → 25 Mar 2015 Conference number: 12th https://www.iacr.org/workshops/tcc2015/ |

### Publication series

Name | Lecture Notes in Computer Science |
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Publisher | Springer |

Volume | 9015 |

ISSN (Print) | 0302-9743 |

ISSN (Electronic) | 1611-3349 |

### Conference

Conference | Theory of Cryptography Conference 2015 |
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Abbreviated title | TCC 2015 |

Country | Poland |

City | Warsaw |

Period | 23/03/15 → 25/03/15 |

Internet address |

## Cite this

*Theory of Cryptography : 12th Theory of Cryptography Conference, TCC 2015 Warsaw, Poland, March 23-25, 2015 Proceedings, Part II*(pp. 378-400). (Lecture Notes in Computer Science; Vol. 9015). Springer. https://doi.org/10.1007/978-3-662-46497-7_15