  Random number has many applications, it plays an important role in quantum
information processing. It's not difficult to generate true random numbers, the
main difficulty is how to certify the random numbers generated by untrusted
devices. In [Nature(London) 464, 1021 (2010)], the authors provided us a way to
generate certified random number by Bell's theorem. In their scheme, we can use
the nonlocal behavior of entangled states to generate certified randomness. But
there are entangled states, which admit a local hidden variable model, could
not be used in their scheme. We show in our paper that the nonlocal
correlations in every entangled state can be used to generate certified
randomness, and we use Werner states as an example to show how to quantify the
output randomness.
