If I am encrypting a file with GCM/AES256 with a weak key (say a sha256), does the fact that it takes time to brute force a long message improve my security?
Example: I use the sha256 of "ARainyDay" to encrypt a 1kB file.
To brute-force it, one must still try and decode my file 5429503678976 times (26^9).
Even considering 1ms/try, it still takes 62841 days. That makes my key more secure then?