  We introduce a mirror copy of the ordinary fermions and Higgs scalars for
embedding the $SU(2)_L\times U(1)_Y$ electroweak gauge symmetry into an
$SU(2)_L\times SU(2)_R\times U(1)_{B-L}$ left-right gauge symmetry. We then
show the spontaneous left-right symmetry breaking can automatically break the
parity symmetry motivated by solving the strong CP problem. Through the
$SU(2)_R$ gauge interactions, a mirror Majorana neutrino can decay into a
mirror charged lepton and two mirror quarks. Consequently we can obtain a
lepton asymmetry stored in the mirror charged leptons. The Yukawa couplings of
the mirror and ordinary charged fermions to a dark matter scalar then can
transfer the mirror lepton asymmetry to an ordinary lepton asymmetry which
provides a solution to the cosmic baryon asymmetry in association with the
$SU(2)_L$ sphaleron processes. In this scenario, the baryon asymmetry can be
well described by the neutrino mass matrix up to an overall factor.
