A method of cyphering, by an integrated processor, of a set of data to be stored in a memory, including performing, in a continuous operation following a data flow, the steps of dividing the data flow into blocks of predetermined size and, for each block: generating a cyphering key using a pseudo-random generator implementing a continuous algorithm of cyphering according to a key specific to the integrated circuit and of an initialization vector changing for each block; combining the data block and the corresponding key in a continuous operation; and storing in the memory each cyphered block and the initialization vector used to cypher it.