A memory device that includes a memory array and a memory controller is introduced. The memory controller is configured to adjust a program strength of the program pulse according to the configurable ratio of the first bit value and the second bit value to generate an adjusted program pulse or to adjust a bias voltage pair according to the configurable ratio of the first bit value and the second bit value to generate an adjusted bias voltage pair. The memory controller is further configured to generate the random bit stream with the configurable ratio of the first bit value and the second bit value according to the data stored in the plurality of memory cells included in the memory array after applying the adjusted program pulse or according to the data stored in the plurality of memory cells after being biased by the adjusted bias voltage pair.