1. A Montgomery exponentiator that modulo exponentiates a generator to a power of an exponent, the Montgomery exponentiator comprising: a first multiplier that is configured to repeatedly square a residue of the generator to produce a series of first multiplier output values at a first multiplier output; and a second multiplier that is configured to multiply selected ones of the series of first multiplier output values that correspond to a bit of the exponent that is a predetermined binary value, by a partial result, to produce a series of second multiplier output values at a second multiplier output.