Method and system for watermarking a USB PD protocol hardware sub-system

A hardware subsystem operatively coupled to a device under test (DUT), said hardware subsystem comprising:

• a watermarking signal detection circuit comprising a multiplexer structure, a look-up table storing key-value pairs mapping combinations of K-codes to predefined packets, and control logic, wherein the watermarking signal detection circuit is configured to:
• detect a watermarking signal transmitted by a tester on a configuration channel (CC) lines coupled to a Type-C port of a Universal Serial Bus (USB) Type-C and Power Delivery (PD) protocol associated with the hardware subsystem, said tester configured to test whether the DUT is watermarked or not, wherein the watermarking signal comprises a custom signaling comprising a combination of K-Codes, other than Start of Packet (SOP) ordered sets defined in the USB Power Delivery Specification;
• automatically assume control via the multiplexer structure to enable direct communication between the watermarking signal detection circuit and a USB Type-C and PD stack and a bus interface, bypassing a System on Chip/Integrated Circuit (SOC/IC) microcontroller associated with the hardware subsystem;
• respond with a response signal, said response signal comprising a pre-defined packet having a vendor identity and a secret code corresponding to the combination of K-codes received;
• wherein the watermarking signal comprises the combination of K-codes;
• transmit the response signal through a buffer in an existing USB Type-C and PD stack, wherein the response signal is fetched through a key-value mechanism comprising a unique code corresponding to the combination of K-codes in the watermarking signal;
• and
• relinquishes control via the multiplexer structure to restore communication between the microcontroller (MCU) and the bus interface and the USB Type-C and PD stack, the microcontroller (MCU) operatively coupled to the DUT once a transmission of the response signal is complete.