Apparatus and method for generating an individual key for accessing a predetermined addressable unit of a memory divided into addressable units. The apparatus includes a calculator for calculating a page pre-key based on a page address, a determiner for determining the individual key based on the page pre-key and a unit address, a memory for storing the calculated page pre-key, and a checker for checking whether during a next access to a further predetermined unit to which a further unique address is associated, an already calculated page pre-key exists in a temporary memory, which has been calculated based on a page address of a unique address, which is identical to the page address of the further unique address, and, if so, transmitting the already calculated page pre-key to the determiner by bypassing the calculator, and, if not, transmitting the page address of the further unique address to the calculator.