  We establish an exact analytical treatment for the determination of the
strengths of the Rashba and Dresselhaus spin-orbit interactions in a single
sample by measuring persistent spin current. A hidden symmetry is exploited in
the Hamiltonian to show that the spin current vanishes when the strength of the
Dresselhaus interaction becomes equal to the strength of the Rashba term. The
results are sustained even in the presence of disorder and thus an experiment
in this regard will be challenging.
