I saw a sample code where the same password is salted with a different value (using PBKDF2) for each encryption. That means that the salt must be stored for each encrypted message.
I don't understand why they do that since AES is used here in CBC mode with a random IV at each encryption, so a same plaintext will not produce the same ciphertext.
My understanding is to use a unique key for all the encryptions made with a same password. That key is produced by salting the password and I store the salt somewhere in cleartext. I though it was enough to do that because salting the password ensures the same password does not generate the same key. So the combination of the salted password and the unique IV are enough.
So my question is: is it a better behaviour to re-salt a password at each encryption?