DSA has two pair of functions: updateSigningParam and sign, updateVerifyingParam and verify. You also have two implementation for updateSigningParam and updateVerifyingParam, a trivial one and one with extra arguments. The extra argument is actually 2^(2*N) mod P. If you have the arguments pre-calculated, call the one with this argument. Otherwise, call the one without the arguments and calculate it on chip with an extra resource.