I need to find a firmware for this device for protected AES implementation.
The “most completed” masked AES I know is for Cortex-M4 (see https://github.com/ANSSI-FR/SecAESSTM32/blob/master/README.md).
However - the RSM used in DPAContestV4 was posted at http://www.dpacontest.org/v4/rsm_doc.php which uses AVR assembly, and I think will be more compatible with the XMEGA. But you’d have to still massage it into our format.
Maybe someone else knows of a more suitable one for the XMEGA?