  keV-scale gauge-singlet fermions, allowed to mix with the active neutrinos,
are elegant dark matter (DM) candidates. They are produced in the early
universe via the Dodelson-Widrow mechanism and can be detected as they decay
very slowly, emitting X-rays. In the absence of new physics, this hypothesis is
virtually ruled out by astrophysical observations. Here, we show that new
interactions among the active neutrinos allow these sterile neutrinos to make
up all the DM while safely evading all current experimental bounds. The
existence of these new neutrino interactions may manifest itself in
next-generation experiments, including DUNE.
