A computing system is described that at least one microphone, a secure processing unit, and a general processing unit. The microphone is coupled to an audio processor configured to receive at least one audio signal from the at least one microphone and generate a first encrypted audio signal and a second encrypted audio signal The secure processing unit is configured to: receive the first encrypted audio signal from the audio processor, decrypt the first encrypted audio signal, and responsive to determining that the first encrypted audio signal includes an unlock command, output an indication of a decryption key. The general processing unit is configured to: receive the second encrypted audio signal from the audio processor, and decrypt the second encrypted audio signal with the decryption key.