A method for reading or writing data at an address of a memory is disclosed. The data includes a number of consecutive words that each has a plurality of bits. The words are transferred to or from the memory in synchronization with a clock signal so that each word is transferred in one cycle of the clock signal. The bits are scrambled or unscrambled by applying a logic function to the bits of each word. The logic function is identical for the scrambling and the unscrambling and makes use of a bit-key that is dedicated to the word and is identical for the scrambling and the unscrambling. Each bit-key comes from a pseudo-random series generated based on the address.