  We propose that the inflaton is coupled to ordinary matter only
gravitationally and that it decays into a completely hidden sector. In this
scenario both baryonic and dark matter originate from the decay of a flat
direction of the minimal supersymmetric standard model (MSSM), which is shown
to generate the desired adiabatic perturbation spectrum via the curvaton
mechanism. The requirement that the energy density along the flat direction
dominates over the inflaton decay products fixes the flat direction almost
uniquely. The present residual energy density in the hidden sector is typically
shown to be small.
