Hello everyone,
I recently purchased the ChipWhisperer Nano development kit to evaluate the side-channel attack (SCA) performance of the newly developed Ladybug AEAD algorithm. I have been following the documentation available on the official ChipWhisperer GitHub to familiarize myself with the platform and the provided AES tests.
Current Setup:
- Target Board: CWLITEARM/STM32F3.
- Capture Board: ChipWhisperer Nano.
- Firmware Changes:
- I added the Ladybug AEAD implementation to
chipwhisperer/firmware/mcuin a newsimpleserial-ladybugfolder. - Updated the makefile to include Ladybug AEAD as a new target.
Progress So Far:
- Successfully compiled the Ladybug AEAD firmware and generated the
.hexfile. - Uploaded the firmware to the STM32F3 target using the programmer:
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Detected known STM32: STM32F302xB(C)/303xB(C)
Extended erase (0x44), this can take ten seconds or more
Attempting to program 16547 bytes at 0x8000000
STM32F Programming flash...
STM32F Reading flash...
Verified flash OK, 16547 bytes
Issue:
When I attempt to capture power traces using my Python script (adapted from the provided AES examples), I encounter an issue with the target acknowledgment (ACK). While I can see the key being set successfully, the target does not always respond correctly during the capture loop. Here is a summary of the log:
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Initializing target communication...
(ChipWhisperer Target WARNING|File SimpleSerial.py:447) Unexpected start to command:
Target version: None
Setting key: 2b7e151628aed2a6abf7158809cf4f3c
(ChipWhisperer Target ERROR|File SimpleSerial.py:351) Target did not ack
Attempt 1/3 failed: Device failed to ack
Target reset and buffer flushed.
Setting key: 2b7e151628aed2a6abf7158809cf4f3c
Key set successfully.
Starting capture loop...
How I Set Up My Main Function:
This is how I implemented the main function on the target device to handle communication with the ChipWhisperer:
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int main() {
// Initialize the platform, UART, and SimpleSerial
platform_init(); // Initialize the platform
init_uart(); // Initialize UART for communication
trigger_setup(); // Initialize trigger pin
simpleserial_init(); // Initialize SimpleSerial protocol
// Register SimpleSerial commands
simpleserial_addcmd('k', 16, set_key); // Key Set command
simpleserial_addcmd('p', 16, simpleserial_encrypt); // Encrypt command
simpleserial_addcmd('c', 16, simpleserial_decrypt); // Decrypt command
printf("Commands registered successfully.\n");
// Loop indefinitely to process commands
while (1) {
simpleserial_get();
}
return 0;
}
Troubleshooting Steps I’ve Tried:
- Synchronization: I added a dummy synchronization step in the main function by sending a version message (‘v’) at startup:
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simpleserial_put('v', 0, NULL); // Indicate readiness
However, the Python script still shows Target version: None.
2. Buffer Flushing: I ensured the target buffer is flushed and reset between commands:
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scope.io.target_pwr = "low"
time.sleep(0.5)
scope.io.target_pwr = "high"
time.sleep(1)
target.flush()
- Retries: Added retry logic for setting the key and capturing traces.
- UART Configuration: Verified that the UART settings on the target match those in the Python script.
Request for Help:
- Has anyone successfully integrated a custom AEAD algorithm with ChipWhisperer?
- What might I be missing in the target or Python script setup to resolve the “did not ACK” issue?
- Are there any specific debugging techniques or tools to identify the root cause of target communication failures?
Any guidance or suggestions would be greatly appreciated!
Thanks in advance!