### Abstract

We investigate coin-flipping protocols for multiple parties in a quantum broadcast setting: We propose and motivate a definition for quantum broadcast. Our model of quantum broadcast channel is new. We discovered that quantum broadcast is essentially a combination of pairwise quantum channels and a classical broadcast channel. This is a somewhat surprising conclusion, but helps us in both our lower and upper bounds. We provide tight upper and lower bounds on the optimal bias ε of a coin which can be flipped by k parties of which exactly g parties are honest: for any 1≤g≤k,ε=1/2-⊖(g/k). Thus, as long as a constant fraction of the players are honest, they can prevent the coin from being fixed with at least a constant probability. This result stands in sharp contrast with the classical setting, where no non-trivial coin-flipping is possible when g ≤ k/2.

Original language | English (US) |
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Title of host publication | Proceedings of the Annual IEEE Conference on Computational Complexity |

Pages | 250-259 |

Number of pages | 10 |

Volume | 19 |

State | Published - 2004 |

Event | Proceedings - 19th IEEE Annual Conference on Computational Complexity - Amherst, MA, United States Duration: Jun 21 2004 → Jun 24 2004 |

### Other

Other | Proceedings - 19th IEEE Annual Conference on Computational Complexity |
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Country | United States |

City | Amherst, MA |

Period | 6/21/04 → 6/24/04 |

### Fingerprint

### ASJC Scopus subject areas

- Computational Mathematics

### Cite this

*Proceedings of the Annual IEEE Conference on Computational Complexity*(Vol. 19, pp. 250-259)

**Multiparty quantum coin flipping.** / Ambainis, Andris; Buhrman, Harry; Dodis, Yevgeniy; Röhrig, Hein.

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

*Proceedings of the Annual IEEE Conference on Computational Complexity.*vol. 19, pp. 250-259, Proceedings - 19th IEEE Annual Conference on Computational Complexity, Amherst, MA, United States, 6/21/04.

}

TY - GEN

T1 - Multiparty quantum coin flipping

AU - Ambainis, Andris

AU - Buhrman, Harry

AU - Dodis, Yevgeniy

AU - Röhrig, Hein

PY - 2004

Y1 - 2004

N2 - We investigate coin-flipping protocols for multiple parties in a quantum broadcast setting: We propose and motivate a definition for quantum broadcast. Our model of quantum broadcast channel is new. We discovered that quantum broadcast is essentially a combination of pairwise quantum channels and a classical broadcast channel. This is a somewhat surprising conclusion, but helps us in both our lower and upper bounds. We provide tight upper and lower bounds on the optimal bias ε of a coin which can be flipped by k parties of which exactly g parties are honest: for any 1≤g≤k,ε=1/2-⊖(g/k). Thus, as long as a constant fraction of the players are honest, they can prevent the coin from being fixed with at least a constant probability. This result stands in sharp contrast with the classical setting, where no non-trivial coin-flipping is possible when g ≤ k/2.

AB - We investigate coin-flipping protocols for multiple parties in a quantum broadcast setting: We propose and motivate a definition for quantum broadcast. Our model of quantum broadcast channel is new. We discovered that quantum broadcast is essentially a combination of pairwise quantum channels and a classical broadcast channel. This is a somewhat surprising conclusion, but helps us in both our lower and upper bounds. We provide tight upper and lower bounds on the optimal bias ε of a coin which can be flipped by k parties of which exactly g parties are honest: for any 1≤g≤k,ε=1/2-⊖(g/k). Thus, as long as a constant fraction of the players are honest, they can prevent the coin from being fixed with at least a constant probability. This result stands in sharp contrast with the classical setting, where no non-trivial coin-flipping is possible when g ≤ k/2.

UR - http://www.scopus.com/inward/record.url?scp=4944255012&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=4944255012&partnerID=8YFLogxK

M3 - Conference contribution

VL - 19

SP - 250

EP - 259

BT - Proceedings of the Annual IEEE Conference on Computational Complexity

ER -