PA_DPA_3 incorrect key

Embedded Security ChipWhisperer Software
1

Hello,

Just a quick question. I’m running CW303 with CW nano. When I capture all the data on PA DPA 3 tutorial I get incorrect key.

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Can someone help me with this and explain why? Thank you.

2

Looks like you’ve got almost half the key right, so you’re on the right path.
Quoting from the notebook:

You may also find that you need to modify gain settings and the number of traces you capture - this attack is much more sensitive to gain settings and noise than a CPA attack would be.

Did you try optimizing your gain settings and capturing more traces?

Jean-Pierre

3

I have tried changing gains and set traces to 7500 but I’m still getting the same answer.

4

Hi Jax,

I’ve found the XMega target to unfortunately be super finicky for this attack and require lots of fine tuning to work even with the CWLite. Two more things you can do to hopefully make the attack work:

  1. Try plotting the difference of means for some of the bytes that failed. It might be the case that a later part of AES is matching. You can use that information to fine tune the trace length and remove the later parts of the algorithm.
  2. You might want to try actually reducing the number of traces you capture. I’ve found there’s typically a sweet spot where the attack works best.

Let me know if either of those work,

Alex