2016/08/12 by Bricout, Rémi, Chailloux, André
#FOS: Physical sciences #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.1608.03820
In this paper, we study relativistic bit commitment, which uses timing and location constraints to achieve information theoretic security. We consider the FQ multi-round bit commitment scheme introduced by Lunghi et al. [LKB+15]. This protocol was shown secure against classical adversaries as long as the number of rounds m is small compared to √(Q) where Q is the size of the used field in the protocol [CCL15,FF16]. In this work, we study classical attacks on this scheme. We use classical strategies for the CHSHQ game described in [BS15] to derive cheating strategies for this protocol. In particular, our cheating strategy shows that if Q is an even power of any prime, then the protocol is not secure when the number of rounds m is of the order of √(Q). For those values of Q, this means that the upper bound of [CCL15,FF16] is essentially optimal.