We study the properties of QCD at high baryon density in a finite volume where color superconductivity occurs. We derive exact sum rules for complex eigenvalues of the Dirac operator at finite chemical potential, and show that the Dirac spectrum is directly related to the color superconducting gap $Δ$. Also, we find a characteristic signature of color superconductivity: an X-shaped spectrum of partition function zeros in the complex quark mass plane near the origin, reflecting the $Z(2)_{L} \times Z(2)_{R}$ symmetry of the diquark pairing. Our results are universal in the domain $Δ^{-1} \ll L \ll m_π^{-1}$ where $L$ is the linear size of the system and $m_π$ is the pion mass at high density.

4 pages, 1 figure; v3. changed figure, added comments and references, final version to appear in Phys. Rev. Lett