### 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 |

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### 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]