Multiparty Quantum Coin Flipping
Abstract
We investigate coin-flipping protocols for multiple parties in a quantum broadcast setting: (1) We propose and motivate a definition for quantum broadcast. Our model of quantum broadcast channel is new. (2) 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. (3) We provide tight upper and lower bounds on the optimal bias epsilon of a coin which can be flipped by k parties of which exactly g parties are honest: for any 1 <= g <= k, epsilon = 1/2 - Theta(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.
Cite
@article{arxiv.quant-ph/0304112,
title = {Multiparty Quantum Coin Flipping},
author = {Andris Ambainis and Harry Buhrman and Yevgeniy Dodis and Hein Roehrig},
journal= {arXiv preprint arXiv:quant-ph/0304112},
year = {2016}
}
Comments
v2: bounds now tight via new protocol; to appear at IEEE Conference on Computational Complexity 2004