= Capture =
== The setup for this capture routine will be pretty straightforward because the firmware is so close to the SimpleSerial targets we've attacked before. Only a small number of modifications need to be made to adapt the capture script for TEA. # First, run the AES SimpleSerial example script (<code>Project > Example Scripts > ChipWhisperer-Lite: AES SimpleSerial on XMEGA</code>). This will connect to the hardware and prepare most of the settings.# Open the programmer (<code>Tools > CW-Lite XMEGA Programmer</code>) and find the hex file that we made in the previous section. Flash this program onto the target. # Under ''Target Settings'', change the ''Input Length'' and ''Output Length'' from 16 to 8 bytes to match the TEA code (64 bit plaintext and ciphertext).# Under ''Scope Settings'', change the trigger offset to 0 samples. All of the other default settings are fine. Before starting the full captures, open the Encryption Monitor (<code>Tools > Encryption Status Monitor</code>) and press ''Capture Setup ==1''. Confirm that the ''Text In'' and ''Text Out'' are 8 bytes long, like we specified above. If you want to test a specific case, when the input and key are both all 0s, the output is <code>41 EA 3A 0A 94 BA A9 40</code>.== Sample Outputs ==For our analysis, we'll need two sets of data. The first should have random keys and plaintexts, and the second should have a fixed ("secret") key and random plaintexts. For this guide, I'll be using a fixed key of <code>00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F</code>. Capture about 1000 traces for each set and put all of the data files in a convenient place.
= Analysis =