the invention concerns a microcontroller intended to be incorporated in a portable object of type smartcard , including at least : a contact stud to supply the said microcontroller with current ; a data input and / or output contact stud ; an efficient data processing part ; and confidential information . according to the invention , the microcontroller also includes : means to vary the supply voltage of the efficient data processing part , the said means being able to secure the said confidential data against current attacks .