A power bus monitor for use in an electronic product is coupled to receive power from an external power supply. The power bus monitor includes a signal detector coupled to an output of the external power supply to receive and demodulate information encoded on the output of the external power supply into a sequence of bits. A decoder is coupled to receive the sequence of bits from the signal detector and decrypt the sequence of bits. A logical comparator is coupled to receive the sequence of bits decrypted by the decoder. The logical comparator is coupled to assert an authentication signal indicating the external power supply is authorized to provide power to the electronic product when the logical comparator recognizes the sequence of bits decrypted by the decoder as a key.