Linux typically stores user names and password hashes in /etc/passwd or /etc/shadow.
Now lets say I have an old CentOS distro and I want to attempt to recover a user's password (it's in a legal, learning context at school) encrypted with DES, I figured I would need a plaintext and a cipher encrypted using the same key as my unknown password, crack said key, then decrypt the cipher stored for said user (right?).
Now, my question is, how/when does Linux generate keys when creating users? Could I assume the key used to be the same if I juste created a new user? If so, is the key used by the system just plain recoverable?