Originally posted by BV1963
Try with no quotes:

ALTER USER yyy IDENTIFIED BY VALUES password_from above query ;
this wont work

Code:
SQL> alter user amar identified by values C5D5B636B43DB0C5;
alter user amar identified by values C5D5B636B43DB0C5
                                     *
ERROR at line 1:
ORA-02153: invalid VALUES password string