US Patent 7168625 Making secure downloaded application in particular in a smart card

The invention concerns a method for differentiating between data and instructions thereby providing against certain attacks in a data processing device such as a smart card, whereby a generator associates a random number with an applicative component of a downloaded application, and a transformer in a virtual machine applies each of the instruction words in the component and the associated random number to a transformation function so as to store the transformed instruction words when downloading the component. A second transformer applies each of the transformed words of part of the component and the associated random number to the reciprocal function of the transformation function so as to retrieve the instruction words constituting the component part, to execute the same.