How long would it take all of the supercomputers or cloud computing on Earth to bruteforce a significantly long password?
A salt is supposed to be publicly available, for instance it needs to be stored in a DB next to the password hash. In that case the time it takes to recover the password is just a brute force or dictionary for the password. If the salt is static then rainbow tables may be used as well for any attack. Now if the password has an entropy of 256 bits then this is obviously not a problem. Actual passwords however only have about 42 bits of entropy on average, and this is why bcrypt is often needed to provide some additional security.
It is of course also possible to use a 256 bit pepper, which is a salt value that is kept secret. In that case &quot;cracking&quot; the hash will require both the password and the pepper. We cannot do that even with quantum computers because the energy requirements would be too high (cracking &gt; 128 bit security against classical computers or &gt; 256 bit against quantum computers is completely infeasible and forever will be).