// Since base will be considered % n, it's okay if base > FLOOR_SQRT_MAX_LONG,
      // so long as n <= FLOOR_SQRT_MAX_LONG.
      return ((n <= FLOOR_SQRT_MAX_LONG) ? SMALL : LARGE).testWitness(base, n);
    }

    /** Returns a * b mod m. */
    abstract long mulMod(long a, long b, long m);

    /** Returns a^2 mod m. */
    abstract long squareMod(long a, long m);