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Revision #1 to TR15-106 | 21st March 2018 17:08
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#### Coin Flipping of Any Constant Bias Implies One-Way Functions

**Abstract:**
We show that the existence of a coin-flipping protocol safe against any non-trivial constant bias (e.g., $.499$) implies the existence of one-way functions. This improves upon a recent result of Haitner and Omri [FOCS '11], who proved this implication for protocols with bias $\frac{\sqrt2 -1}2 - o(1) \approx .207$. Unlike the result of Haitner and Omri, our result also holds for weak coin-flipping protocols.

**Changes to previous version:**
Simplifications and structure changes in section 4.

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TR15-106 | 22nd June 2015 11:02
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#### Coin Flipping of Any Constant Bias Implies One-Way Functions

**Abstract:**
We show that the existence of a coin-flipping protocol safe against any non-trivial constant bias (e.g., $.499$) implies the existence of one-way functions. This improves upon a recent result of Haitner and Omri [FOCS '11], who proved this implication for protocols with bias $\frac{\sqrt2 -1}2 - o(1) \approx .207$. Unlike the result of Haitner and Omri, our result also holds for weak coin-flipping protocols.