  We present a gauge-independent quark mass counterterm for the on-shell
renormalization of the Cabibbo-Kobayashi-Maskawa (CKM) matrix in the Standard
Model that is directly expressed in terms of the Lorentz-invariant self-energy
functions, and automatically satisfies the hermiticity constraints of the mass
matrix. It is very convenient for practical applications and leads to a
gauge-independent CKM counterterm matrix that preserves unitarity and satisfies
other highly desirable theoretical properties, such as flavor democracy.
