The present technology relates to a signal processing device, and a signal processing method for enabling reduction of a processing load while ensuring safety. The signal processing device includes a control unit that acquires designation information indicating a designated portion to be encrypted in output data and an encryption processing unit that encrypts the designated portion indicated by the designation information in the output data using a key. Furthermore, the designated portion indicated by the designation information is changed with time. The present technology can be applied to an in-vehicle camera.