You can apply a new external encryption key to a Derby database by specifying the newEncryptionKey attribute on the connection URL when you boot the database.
To encrypt a database with a new external encryption key:
jdbc:derby:salesdb;encryptionKey=6162636465666768;newEncryptionKey=6862636465666768'
If authentication and SQL authorization are both enabled, the credentials of the database owner must be supplied as well, since encryption is a restricted operation.
If you disabled log archival before you applied the new encryption key, create a new backup of the database after the database is reconfigured with the new encryption key. For more information, see the section "Backing up and restoring databases" in the Derby Server and Administration Guide, particularly "Roll-forward recovery".