def calculate_a(self):
        """
        Calculate the client's public value A = g^a%N
        with the generated random number a
        :param {Long integer} a Randomly generated small A.
        :return {Long integer} Computed large A.
        """
        big_a = pow(self.g, self.small_a_value, self.big_n)
        # safety check
        if (big_a % self.big_n) == 0:
            raise ValueError('Safety check for A failed')
        return big_a
Calculate the client's public value A = g^a%N
        with the generated random number a
        :param {Long integer} a Randomly generated small A.
        :return {Long integer} Computed large A.