
An AlmostOptimally Fair ThreeParty CoinFlipping Protocol
In a multiparty fair coinflipping protocol, the parties output a common...
read it

A Tight Lower Bound on Adaptively Secure FullInformation Coin Flip
In a distributed coinflipping protocol, Blum [ACM Transactions on Compu...
read it

Quantum Weak Coin Flipping
We investigate weak coin flipping, a fundamental cryptographic primitive...
read it

Tighter Bounds on MultiParty Coin Flipping via Augmented Weak Martingales and Differentially Private Sampling
In his seminal work, Cleve [STOC '86] has proved that any rround coinf...
read it

Private Aggregation from Fewer Anonymous Messages
Consider the setup where n parties are each given a number x_i ∈F_q and ...
read it

Improved Summation from Shuffling
A protocol by Ishai et al. (FOCS 2006) showing how to implement distribu...
read it

SWIFT: Superfast and Robust PrivacyPreserving Machine Learning
Performing ML computation on private data while maintaining data privacy...
read it
Fair Coin Flipping: Tighter Analysis and the ManyParty Case
In a multiparty fair coinflipping protocol, the parties output a common (close to) unbiased bit, even when some adversarial parties try to bias the output. In this work we focus on the case of an arbitrary number of corrupted parties. Cleve [STOC 1986] has shown that in any such mround coinflipping protocol, the corrupted parties can bias the honest parties' common output bit by Θ(1/m). For more than two decades, the best known coinflipping protocol was the one of Awerbuch et al. [Manuscript 1985], who presented a tparty, mround protocol with bias Θ(t/√(m)). This was changed by the breakthrough result of Moran et al. [TCC 2009], who constructed an mround, twoparty coinflipping protocol with optimal bias Θ(1/m). Haitner and Tsfadia [STOC 2014] constructed an mround, threeparty coinflipping protocol with bias O(log^3m / m). Still for the case of more than three parties, the best known protocol remained the Θ(t/√(m))bias protocol of Awerbuch et al. We make a step towards eliminating the above gap, presenting a tparty, mround coinflipping protocol, with bias O(t^4 · 2^t ·√(log m)/m^1/2+1/(2^t12)) for any t≤12 loglog m. This improves upon the Θ(t/√(m))bias protocol of Awerbuch et al., and in particular, for t∈ O(1) it is an 1/m^1/2 + Θ(1)bias protocol. For the threeparty case, it is an O(√(log m)/m)bias protocol, improving over the O(log^3m / m)bias protocol of Haitner and Tsfadia. Our protocol generalizes that of Haitner and Tsfadia, by presenting an appropriate recovery protocol for the remaining parties to interact in, in the case that some parties abort or are caught cheating. We prove the fairness of the new protocol by presenting a new paradigm for analyzing fairness of coinflipping protocols.
READ FULL TEXT
Comments
There are no comments yet.