USB Power analysis with PhyWhisperer

Embedded Security Side Channel Power Analysis
1

Dear Forum Members,

I am currently conducting power analysis on a USB device and have encountered an issue with the measurement setup. According to the PhyWhisperer schematics, the “Shunt Out” connector is directly connected to the Vcc of the USB device. Consequently, the measurement from the “Shunt Out” connector captures the USB voltage rather than the power consumption of the device.

Even after adjusting the J4 jumpers, which adds a resistor between the voltage source and the device, I am unable to measure the actual power consumption.

Could someone please clarify what I might be overlooking in this setup?
Additionally, I would appreciate any guidance on how to accurately measure the power consumption of the USB device.

Thank you for your assistance.

Best regards,
John

2

The shunt out isn’t meant to accurately measure power consumption. The rationale for this is that side-channel power attacks don’t need accurate measurements; relative measurements suffice.

So, PhyWhisperer + a ChipWhisperer capture device allows you to measure small variations in the USB Vcc line, which can be applied to side-channel attacks. If you want to accurately measure a USB device’s power consumption, you need a different tool (and many exist to do exactly that).