This a very old post. But I think it is good to document a solution.
It's OpenSource
The encryption and decryption algorithms are in the file:
"feng_community/application/Functions.php"
However. If you have other users on Feng and you have access to the database, it is easier to modify the table "og_users".
Here you can assign administrator permissions to another user.
Set the field "type" = admin
and all the fields "can-*" = 1 on the selected user' row.
Then you log in as that user and make any necessary changes.