  We demonstrate how radio pulsars can be used as random number generators.
Specifically, we focus on publicly verifiable randomness (PVR), in which the
same sequence of trusted and verifiable random numbers is obtained by multiple
parties. PVR is a critical building block for many processes and algorithms
(including cryptography, scientific trials, electoral audits and international
treaties). However, current approaches (based on number theory) may soon become
vulnerable to quantum computers, motivating a growing demand for PVR based on
natural physical phenomena. In this context, we explore pulsars as a potential
physical PVR source. We first show that bit sequences extracted from the
measured flux densities of a bright millisecond pulsar can pass standardised
tests for randomness. We then quantify three illustrative methods of
bit-extraction from pulsar flux density sequences, using simultaneous
observations of a second pulsar carried out with the Parkes telescope in
Australia and the Five-hundred-metre Aperture Spherical radio Telescope (FAST)
in China, supported by numerical simulations. We demonstrate that the same bit
sequence can indeed be obtained at both observatories, but the ubiquitous
presence of radiometer noise needs to be accounted for when determining the
expected bit error rate between two independent sequences. We discuss our
results in the context of an imaginary use-case in which two mutually
distrusting parties wish to obtain the same random bit sequence, exploring
potential methods to mitigate against a malicious participant.
