A system and method is described in which protected memory writes are achieved in single transaction without leaving open a window in time for erroneous data to corrupt space in a target register. A single data packet preferably includes both user data to be written to a target storage device or location as well as the key data for authorizing the writing of such user data. Key data is preferably calculated by manipulating user data contained in the same packet or transmission thereby simplifying a verification process conducted the controller associated with target storage location.