carry = carry_add(data, buf, carry, i);
        }

        if (carry != 0) {
            for (int i = outlen - 1; i >= 0; i--) {
                carry += buf[i] & 0xff;
                buf[i] = (byte) (carry & 0xff);
                carry >>>= 8;
            }
        }
        return buf;
    }

    private static int carry_add(byte[] data, byte[] out, int c, int i) {