  In this paper, we use the information-theoretic approach to study
curvature-dimension condition, rigidity theorems and entropy differential
inequalities on Riemannian manifolds. We prove the equivalence of the ${\rm
CD}(K, m)$-condition for $K\in \mathbb{R}$ and $m\in [n, \infty]$ and some
entropy differential inequalities along the geodesics on the Wasserstein space
over a Riemannian manifold. The rigidity models of the entropy differential
inequalities are the $K$-Einstein manifolds and the $(K, m)$-Einstein manifolds
with Hessian solitons. Moreover, we prove the monotonicity and rigidity theorem
of the $W$-entropy along the geodesics on the Wasserstein space over Riemannian
manifolds with CD$(0, m)$-condition. Finally, we compare our work with the
synthetic geometry developed by Lott-Villani and Sturm.
