Storing values sent via simpleserial_write?

1

Hey, wanted to ask regarding simpleserial.
I’m using simpleserial-base, I can send an array to the chipwhisperer, like this:

msg = bytearray([0] * 32) 
target.simpleserial_write('p', msg)
print(target.simpleserial_read('r', 32))

and on the chipwhisperer in get_pt() : simpleserial_put('r', 32, pt);

and i get back the array.

I want to ask, how is it possible to store this value as a variable on the chipwhisperer, so that i can expose it and use it in other functions.

Or is it simply stored in “pt” and can be used in other functions?

Regards

2

What do you mean by “on the chipwhisperer”? Are you referring to:

  1. The target? That’s up to you, you can implement this as you wish in the target’s firmware.
  2. The capture unit? Not really.
  3. The host software? This is trivial; it’s what we do in most/all of our notebooks. The cw.capture_trace() function returns a Trace object which contains not only the power measurements but the key, plaintext, and ciphertext associated with that measurement.
4

Thank you for the answer.

I just want to have the bytearray that I send using python/simpleserial to the target board (dummy value [0]*32 ) as a usable variable (array of 32 elements) in my simpleserial-base.c, but i don’t understand how exactly this works, namely, how to access pt and how to later convert it to format i need (int array).

I think if I can somehow access the value of pt on my target board and save it as a global(?) variable on the target, it will not be hard to convert it to the format I need.

Sorry if this is very trivial, but could you give me a pointer?

5

Yup, you can fairly easily save pt as a global variable. As an example:

#define PT_LEN 32
uint8_t PT_GLOBAL[PT_LEN] = {0};
uint8_t get_pt(uint8_t* pt, uint8_t len)
{
    memcpy(PT_GLOBAL, pt, PT_LEN);
    simpleserial_put('r', PT_LEN, pt);
    return 0x00;
}

EDIT: Fixed simpleserial_put call

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