9810067v3

related topics
{key, protocol, security}
{time, systems, information}
{alice, bob, state}
{theory, mechanics, state}

Coin Tossing is Strictly Weaker Than Bit Commitment

Adrian Kent

abstract: We define cryptographic assumptions applicable to two mistrustful parties who each control two or more separate secure sites between which special relativity guarantees a time lapse in communication. We show that, under these assumptions, unconditionally secure coin tossing can be carried out by exchanges of classical information. We show also, following Mayers, Lo and Chau, that unconditionally secure bit commitment cannot be carried out by finitely many exchanges of classical or quantum information. Finally we show that, under standard cryptographic assumptions, coin tossing is strictly weaker than bit commitment. That is, no secure classical or quantum bit commitment protocol can be built from a finite number of invocations of a secure coin tossing black box together with finitely many additional information exchanges.

oai_identifier:
oai:arXiv.org:quant-ph/9810067
categories:
quant-ph cs.CR
comments:
Final version; to appear in Phys. Rev. Lett
doi:
10.1103/PhysRevLett.83.5382
arxiv_id:
quant-ph/9810067
journal_ref:
Phys.Rev.Lett. 83 (1999) 5382-5384
report_no:
DAMTP-1998-123
created:
1998-10-22
updated:
1999-10-29

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