  An extension of the Standard Model with a hidden sector which consists of
gauge singlets (a Dirac fermion $\chi$ and a scalar $S$) plus a vector boson
$V_\mu$ (dark massive photon) is studied. The singlet scalar interacts with the
Standard Model sector through the triple and quartic scalar interactions, while
the singlet fermion and vector boson field interact with the Standard Model
only via the singlet scalar. The scalar field generates the vector boson's
mass. Perspectives for future $e^{-}e^{+}$ colliders is considered.
