Homeplug Green PHY Implementation with Certificate

First of all I want introduce myself: I am Software Development Engineer and I am going ahead to implement Homeplug Green PHY into an e-mobility charger.

Have studied all standards ISO 15118-1, ISO 15118-2, ISO 15118-3 and in addition the specification “HomePlug Green PHY Specification Release Version 1.1.1”. In principle all contents are clear. Then I did some investigations with a real car which already has a interface following the mentioned standards. But the symbols which were peridically send by the car do not fit to any of the patterns discribed in the standards. I assume that for safety reasons an encrypted communication is implemented. But even the encrypted mode is well defined in the standard. For my understanding the encryption is only applied to the payload of the messages but not to other parts of the communication. For e.g. an encrypted message should begin with the sequence 0x00 0x01.

Has anybody experiences with this matter and can give me hint how to handle Homeplug Green PHY protocols with encryption?