Assuming I already have a 256-key (32 char password) for AES encryption, comprised of random alpha-numeric characters and punctuation (95 possible ascii chars), generated by a decent PRNG, is there any reason to use a KDF to convert this into another key of the same length? Is a derivative hash in some way stronger?
Obviously if a password was shorter than the intended key-length, or if the password was predictable (ie, memorizable), I can see how a KDF would be useful. But given the above circumstances, I reason that a KDF (like BCrypt of PBKDF2) would actually reduce the character-range of the key (to 64 chars in bcrypt, and 16 chars in PBKDF2), effectively increasing the chance of a brute-force attack (however unlikely). Any insights?