Abstract: A method including generating an initialization vector, then producing a new mask using the generated initialization vector and using a secret key, masking a datum to be written to an internal cache memory using the constructed new mask, to obtain a masked datum, storing, in a given word of the internal cache memory, the masked datum and the generated initialization vector, and unmasking the masked datum, this including extracting the initialization vector contained in the word, reconstructing the mask using the extracted initialization vector and using the secret key, then unmasking the masked datum using the new mask thus reconstructed.