The current encryption password can be verified by running the following as root:
vdc cryptfs verifypw <password>
The encryption password can be changed by running the following as root:
vdc cryptfs changepw <new_password>
I enjoy PA's decoupling of the encryption and lock screen passwords. Once encryption has been set up, the lock screen pin/password can be changed independently of the encryption password. I am requesting to augment this feature by allowing the user to change the encryption password as well, possibly via a new option in the Encryption section of Settings -> Security.