If a user loses a password for the encryption key, the key custodian must drop the user’s copy of the encryption key and issue to the user another copy of the encryption key with a new password.
alter encryption key key1 drop encryption for user bill
alter encryption key key1 with passwd 'MotherofSecrets' add encryption with passwd 'over2bill' for user bill
alter encryption key key1 with passwd 'over2bill' modify encryption with passwd 'billsnupasswd'