On the basis of the formalism of noncommutative harmonic analysis on the cu
be symmetry group, the canonical forms of boundary value equations of the d
iffraction by a perfectly conducting cube are obtained in the case of prima
ry field with symmetries. Results of realization of the canonical farms in
the problems of diffraction of a plane wave and excitation of a cube by a d
ipole for lambda/a less than or equal to 8, where lambda is the wavelength
and a is the size of the cube edge, are presented.