Unable to connect to Oracle 12c

Hi,

We have recently upgraded the database from Oracle 11g to 12c. However the application developed using CodeIgniter2 throws exception upon logging in. Please see the error below:

ERROR - 2017-07-12 16:50:35 --> Severity: Warning --> oci_connect(): ORA-28040: No matching authentication protocol /system/database/drivers/oci8/oci8_driver.php 230

It looks like the database driver of CodeIgniter does not support Oracle 12c. Please advise what would be the solution for the issue. 
Thanks in advance. 

Regards,
Steven