hardware

July 16, 20241 minute

We accessed the embedded device’s asynchronous serial debugging interface while it was operational and captured some messages that were being transmitted over it. Can you decode them?

Provided files: debugging_interface_signal.sal

To open the .sal file we will use Saleae.

In my case, on Arch, I installed it with yay

yay -S saleae-logic

Once installed, we open it and import the file provided by HackTheBox.

To find the byte rate, we go to the beginning of the connection

We see 32.02 µs, which is 32.02 microseconds.

The Async Serial analyzer asks for the rate per second, so we do a simple calculation

$ python3 -c "print(round(1000000 / 32.02))"

31230

And now we can see the flag