  In this paper, we prove classical coin-flipping secure in the presence of
quantum adversaries. The proof uses a recent result of Watrous [Wat09] that
allows quantum rewinding for protocols of a certain form. We then discuss two
applications. First, the combination of coin-flipping with any non-interactive
zero-knowledge protocol leads to an easy transformation from non-interactive
zero-knowledge to interactive quantum zero-knowledge. Second, we discuss how
our protocol can be applied to a recently proposed method for improving the
security of quantum protocols [DFL+09], resulting in an implementation without
set-up assumptions. Finally, we sketch how to achieve efficient simulation for
an extended construction in the common-reference-string model.
