  A simple protocol which takes advantage of the inherent random times of
detections in single photon counting modules is presented for random active
basis choices when using entanglement-based protocols for Quantum Key
Distribution (QKD). It may also be applicable to the BB84 protocol in certain
cases. The scheme presented uses the single photon detectors already present on
a QKD setup, working on the same rate as the system is capable of detecting,
and is, therefore, not limited by the output rates of quantum random number
generators. This protocol only requires small hardware modifications making it
an attractive solution. We perform a proof-of-principle experiment employing a
spontaneous parametric down-conversion process in a $\chi^{(2)}$ non-linear
crystal to demonstrate the feasibility of our scheme, and show that the
generated sequence passes randomness tests.
