### Abstract

A stream cipher is an important class of encryption algorithms. Its safety depends on the structure of the pseudorandom number generator used. There are various types of pseudo-random number generators in existence, and attack algorithms used on them have been studied individually. In this paper, we express the problem of attacks on a general stream cipher as a probabilistic inference problem, and formulate the optimal key estimation. We also propose a unified framework of attack algorithms that can be applied to a wide variety of stream ciphers. The optimal key estimation, however, has computational complexity. To reduce the complexity, an approximation algorithm based on a probabilistic inference is proposed. We also describe some attack algorithms used on practical pseudorandom number generators. Finally, the proposed algorithm is evaluated by through a computer simulation.

Original language | English |
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Title of host publication | 2012 International Symposium on Information Theory and Its Applications, ISITA 2012 |

Pages | 531-535 |

Number of pages | 5 |

Publication status | Published - 2012 |

Event | 2012 International Symposium on Information Theory and Its Applications, ISITA 2012 - Honolulu, HI Duration: 2012 Oct 28 → 2012 Oct 31 |

### Other

Other | 2012 International Symposium on Information Theory and Its Applications, ISITA 2012 |
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City | Honolulu, HI |

Period | 12/10/28 → 12/10/31 |

### Fingerprint

### ASJC Scopus subject areas

- Computer Science Applications
- Information Systems

### Cite this

*2012 International Symposium on Information Theory and Its Applications, ISITA 2012*(pp. 531-535). [6400993]

**The optimal key estimation of stream ciphers and its approximation algorithm based on a probabilistic inference.** / Iikubo, Yuji; Horii, Shunsuke; Matsushima, Toshiyasu.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*2012 International Symposium on Information Theory and Its Applications, ISITA 2012.*, 6400993, pp. 531-535, 2012 International Symposium on Information Theory and Its Applications, ISITA 2012, Honolulu, HI, 12/10/28.

}

TY - GEN

T1 - The optimal key estimation of stream ciphers and its approximation algorithm based on a probabilistic inference

AU - Iikubo, Yuji

AU - Horii, Shunsuke

AU - Matsushima, Toshiyasu

PY - 2012

Y1 - 2012

N2 - A stream cipher is an important class of encryption algorithms. Its safety depends on the structure of the pseudorandom number generator used. There are various types of pseudo-random number generators in existence, and attack algorithms used on them have been studied individually. In this paper, we express the problem of attacks on a general stream cipher as a probabilistic inference problem, and formulate the optimal key estimation. We also propose a unified framework of attack algorithms that can be applied to a wide variety of stream ciphers. The optimal key estimation, however, has computational complexity. To reduce the complexity, an approximation algorithm based on a probabilistic inference is proposed. We also describe some attack algorithms used on practical pseudorandom number generators. Finally, the proposed algorithm is evaluated by through a computer simulation.

AB - A stream cipher is an important class of encryption algorithms. Its safety depends on the structure of the pseudorandom number generator used. There are various types of pseudo-random number generators in existence, and attack algorithms used on them have been studied individually. In this paper, we express the problem of attacks on a general stream cipher as a probabilistic inference problem, and formulate the optimal key estimation. We also propose a unified framework of attack algorithms that can be applied to a wide variety of stream ciphers. The optimal key estimation, however, has computational complexity. To reduce the complexity, an approximation algorithm based on a probabilistic inference is proposed. We also describe some attack algorithms used on practical pseudorandom number generators. Finally, the proposed algorithm is evaluated by through a computer simulation.

UR - http://www.scopus.com/inward/record.url?scp=84873548587&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84873548587&partnerID=8YFLogxK

M3 - Conference contribution

SN - 9784885522673

SP - 531

EP - 535

BT - 2012 International Symposium on Information Theory and Its Applications, ISITA 2012

ER -