An M6 block cipher system and method for encoding content and authenticating a device may use an M6 core. The M6 block cipher system may include a rotate constant selector selecting one or more rotate constants from a plurality of input rotate constants for output based on a selection signal input thereto, a rotate constant ordering device ordering the selected rotate constants and a common rotate constant input thereto based on a received ordering signal and an M6 core generating one or more of an output signal, a validity signal and a round number based on the ordered rotate constants and a plurality of input signals. The system may include a rotate constant scheduler outputting the ordering signal to the rotate constant ordering device in response to the selection signal and the round number.