I just tested the script using Python 3.9 (with most recent version of fastecdsa and bit) and i experience same problem. Additionally, on line 45 you forget to add equal symbol.
ok, I will try upgrade by python to 3.9 and test again my WSL python is 3.8
What? I said i experience
same problem, which means i also got
same error message.
Can you help to explain each value on shiftdown function for non-programmer understand?
I'm not experienced with cryptography, so i barely can explain it. You could try ask @NotATether or wait someone else giving you an explanation.