1. Read the Python code.2. See parts of key in variables key_part*.3. Find the function check_key().4. See that length of entered key should be the same to key_full_template_trial, which consists of variables key_part*.5. Make a dummy key "VishwaCTF{m4k3_it_possibl3_xxxxxxxx}".6. In check_key() function in "else" block see the verification of the entered key:"if key[i] != hashlib.sha256(username_trial).hexdigest()[4]:"7. Insert "print" in every "if" block to see what is expected:print(f"invalid 4, {key[i]} {hashlib.sha256(username_trial).hexdigest()[4]}")Here we will get the fourth "x" in our dummy key.8. After each "if" change the appropriate "x" to the expected symbol.
Flag: VishwaCTF{m4k3_it_possibl3_b7cdc517}.