1. A method of updating at least a part of a 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 the steps of: determining a first subset of said plurality of memory blocks that require an update from respective current memory block contents to respective updated memory block contents, and a second subset of the plurality of memory blocks having stored therein respective current memory contents that remain unchanged by said updating; calculating a first and a second integrity protection data item over the plurality of 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; 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; and wherein calculating the first and the second integrity protection data items is performed as parallel processes; and updating said first subset of memory blocks with said respective updated memory block contents and storing said first subset of memory blocks to the memory.