I want to run the default aes-128 in CW305 at 50MHz-100MHz frequency. When I change the frequency using target.pll.pll_outfreq_set(100E6, 1), the encryption goes well for sometime but after few iterations, I see errors as follows:
Is there any way to avoid that? . For my purpose, its okay for me if I can not recevie the trace, but I need the encryption running at 100MHz, I am probing with oscilloscope.
On the cw-lite FPGA bitfile that’s currently on the develop branch, I’m able to capture reliably well beyond 105 MHz. Perhaps you’re using an older release with a different bitfile that doesn’t perform as well? It was last updated here, 4 months ago.
But if you’re not using cw-lite to capture the trace, then this is irrelevant; simply remove the cw-lite from your setup and use the CW305 in standalone mode with your other oscilloscope.
@jpthibault if i need to ignore cw-lite scope then I think i will have to get rid of scope definition defined in this notebook. If so, how do i send plaintext and receive encrypted text using ret = cw.capture_trace(scope, target, text, knownkey)
I can use some other UART module but is there any way to use the same/similar python code we are using to send and receive data to/from CW305, by just ignoring scope? I think i can not use the function ret() when I am trying to use cw305 without cw-lite.
@jpthibault I have found a way to communicate, using the functions defined in CW305.py (such as fpga_read, fpga_write) and avoiding arm(). But I am having some confusion regarding the cw305_aes_defines.v.
what is the difference between REG_CRYPT_TEXTIN and REG_CRYPT_CIPHERIN?
Can you take a look at the following sequence if I am doing it correctly:
set_key in REG_CRYPT_KEY->set_plaintext in REG_CRYPT_TEXTIN->set REG_CRYPT_GO to 1-> check is_done() → read REG_CRYPT_CIPHEROUT.
I saw the explanation of REG_CRYPT_GO somewhere but can’t find again. if possible can you please explain the behavior of this reg in brief?
It’s quite straightforward: take out the scope object from your notebook, then look at what cw.capture_trace() does: chipwhisperer/software/chipwhisperer/__init__.py at develop · newaetech/chipwhisperer · GitHub
Make your own custom capture function from capture_trace() by taking out the scope calls there and you’re basically done.
The CW305 whitepaper is probably where you saw the REG_CRYPT_GO explanation. CW305.py handles all this for you, scope or no scope.
It should also be quite straightforward to understand the register definitions from the source code.
Did you figure it out and create your capture_trace() function without scope? if so can you please guide me through it?
@Achraf_hebheb yes I have figured it out. in the original capture_trace() function, there are some dependencies on scope(). you need to get rid of those dependencies and you should be good to go.
