Backing up a fully encrypted database is the same as normal, unencrypted databases, since the encryption process is performed transparently.
To load a back-up dump of an encrypted database, it must use the same encryption key that was used to encrypt the dump.
The database encryption key is stored in the master database, outside of the database you are backing up. For this reason, the backup process is not automatically applied to the database encryption key when you execute the dump database command; you must independently back up the database encryption key and the master key separately from the database backup.