Tight bounds for classical and quantum coin flipping
TCC'11 Proceedings of the 8th conference on Theory of cryptography
Exact Quantum Algorithms for the Leader Election Problem
ACM Transactions on Computation Theory (TOCT)
Semi-loss-tolerant strong coin flipping protocol using EPR pairs
Quantum Information & Computation
On the existence of loss-tolerant quantum oblivious transfer protocols
Quantum Information & Computation
Communications of the ACM
Lower bounds for quantum oblivious transfer
Quantum Information & Computation
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Coin flipping is a fundamental cryptographic primitive that enables two distrustful and far apart parties to create a uniformly random bit. Quantum information allows for protocols in the information theoretic setting where no dishonest party can perfectly cheat. The previously best-known quantum protocol by Ambain is achieved a cheating probability of at most 3/4. On the other hand, Kitaev showed that no quantum protocol can have cheating probability less than 1/sqrt{2}. Closing this gap has been one of the important open questions in quantum cryptography. In this paper, we resolve this question by presenting a quantum strong coin flipping protocol with cheating probability arbitrarily close to 1/sqrt{2}.More precisely, we show how to use any weak coin flipping protocol with cheating probability 1/2+epsilon in order to achieve a strong coin flipping protocol with cheating probability 1/sqrt{2}+O(epsilon). The optimal quantum strong coin flipping protocol follows from our construction and the optimal quantum weak coin flipping protocol described by Mochon.