We should document how to safely decrypt Aria tables. The documentation doesn't currently say:

https://mariadb.com/kb/en/library/encrypting-data-for-aria/

As far as I can tell, an Aria table is only non-encrypted if aria_encrypt_tables=OFF was set when it was created. To decrypt an existing encrypted Aria table, it looks like you need to do the following:

1.) Set aria_encrypt_tables=OFF.

SET GLOBAL aria_encrypt_tables=OFF;

Make sure to also set it in the configuration file.

2.) Find all Aria tables that use the PAGE row_format:

SELECT TABLE_SCHEMA, TABLE_NAME 

FROM information_schema.TABLES 

WHERE ENGINE='Aria' 

AND ROW_FORMAT='PAGE'

AND TABLE_SCHEMA != 'information_schema';

3.) For each table in the results,rebuild the table:

ALTER TABLE aria_tab ENGINE=Aria ROW_FORMAT=PAGE;