A method, system, and program key-controlled object-based memory protection are provided. A processing unit includes an authority check for controlling access by the processing unit to pages of memory according to whether a hardware protection key set currently loaded in an authority mask register allows access to the pages. In particular, each page of memory is assigned a page key number that indexes into the hardware protection key set. The currently loaded hardware protection key set specifies those page key numbers that are currently accessible to the processing unit for the execution context. Each hardware key within the hardware protection key set may be associated with a particular data object or group of data objects. Thus, effectively, the currently loaded hardware protection key set identifies which data objects or groups of data objects are currently accessible. Software keys are assigned to data objects and dynamically mapped to hardware protection key sets, such that when a module is called, the software keys assigned to that module are mapped to the hardware protection key set to be loaded for controlling current access to memory.