Stagegate #2

Embedded Security Capture The Flag (CTF)
1

Hi,

I’m trying to get the flag for the #2 Stagegate challenge, the CPA with some random jitter before very round of the AES encryption.

I’ve downloaded ChipWhisperer Analyzer, and I guess I can see where the random jitters stands (between the huge spikes, the straight linear block). However, I can’t find a way to crop them away. Actually, with the peak detect preprocessing method, I’m able to find the 2 first bytes of the key (according to the known key records).

Is anyone able to help me a bit on how to get rid of the random jitter ? I think I need a resync preprocessing, but I can’t figure out how they work.

Thank you in advance,

Matlink

2

Hello Matlink,

Sorry for the delay.
Try using the SoD preprocessing module. You will need to select a reference window (usually a peak) and an input window where the tool wil try to shift the other traces.
It is possible to crop the traces using the new Record Widget, but it is not really needed since you can select the window in the attack settings.

Regards,
Adriel
SWE at NewAE

3

This new tutorial may help you with this issue (click in the SAD link):
wiki.newae.com/CW-Analyzer_Tool