CWLiteArm - Sawtooth course of Traces


#1

Hello,

The Chipwhisperer creates a Sawtooth course with a period of about 1 min.
I created a similar topic a few days ago “Sawtooth course of Single Point of Trace - ChipWhisperer LiteArm” but with further investigation i became further results.

I tried a lot of different capture settings:
Now:

  • gain.db = 25
  • adc.samples = 600
  • clock.adc_src = “clkgen_x1”
    (changed the settings directly in the library)
    The reset of the settings is default.

I executed 500 “nop” instruction and and took the mean of the Power Trace, this i have done for 20000 Traces.

import numpy as np
import matplotlib.pyplot as plt

traces = np.load(‘traces.npy’)

def mean2():
trace = traces[:, 20:500]
trace1 = np.abs(trace)
mean = np.mean(trace1, axis=1)
plt.plot(mean)
plt.show()

Plot of a Single Power Trace:
noppowertrace

Mean of Power Trace over 20000 Traces:

With a second Chipwhisperer LiteArm I became the same results, so it should not be a defective hardware.
For a test I also added some delays inside the capture script and noticed that the period became smaller (less traces per Period) so it has constant time.

I also tested it with a Chipwhisperer CW303 with the same setup, there i do not get the sawtooth course.

CW303 Mean of Power Trace
cw303_capture

I added the Src-files as an appendix

Thank you for your help.

srcfiles.zip (2.2 KB)


Sawtooth course of Single Point of Trace - ChipWhisperer LiteArm