code: public static BigInteger modPowInsecure(BigInteger base, BigInteger exponent,
        BigInteger modulus) {
      if (modulus.signum() <= 0) {
        throw new ArithmeticException("modulus must be positive");
      }
      return INSTANCE.get().modPowInsecureImpl(base, exponent, modulus);
    }
docs: Calculate (base ^ exponent) % modulus; faster, VULNERABLE TO TIMING ATTACKS.
  
  @param base the base, must be positive
  @param exponent the exponent
  @param modulus the modulus
  @return the (base ^ exponent) % modulus
  @throws ArithmeticException if modulus is non-positive, or the exponent is negative and the
  base cannot be inverted