A method of updating memory content stored in a memory of a processing device, the memory comprising a plurality of addressable memory blocks, the memory content being protected by a current integrity protection data item stored in the processing device, the method comprising determining a first subset of memory blocks that require an update, and a second subset of memory blocks that remain unchanged by said updating; calculating, as parallel processes, a first and a second integrity protection data item over the memory blocks; wherein the first integrity protection data item is calculated over the current memory contents of the first and second subsets of memory blocks; and wherein the second integrity protection data item is calculated over the current memory contents of the second subset of memory blocks and the updated memory block contents of the first subset of memory blocks.