Transitioning from Rijndael from Phalcon 2 to 3.x

We're upgrading an existing install from Phalcon 2 to 3 as part of a PHP Upgrade, and one of the issues that has appeared is the lack of rijndael from 2 to 3, although the docs state that its officially defined (or at least adopted) as AES-256. Is there any way to restore support for Rijndael, or does using AES provide compatibility?

This issue mostly stems from us wanting to minimize the impact of users with existing Cookies/Session data once we upgrade, and if this is something we will not be able to address, any workaround would be beneficial.

My guess would be that AES-256 and Rijndael are the same thing. It shouldn't be too hard to test.