DDSSEC_ — Multiple DataReaders per topic on secured Participant

Looking at the datareader_crypto parameter description of the preprocess_secure_submsg operation:

"If secure_submessage_category is DATAWRITER_SUBMESSAGE, the datareader_crypto shall be the DatareaderCryptoHandle returned by a previous call to register_local_datareader for the DataReader that is the destination of the RTPS Submessage."

It seems that only a single DatareaderCryptoHandle can be returned. This implies that a secure DATAWRITER_SUBMESSAGE should be at destination of a single DataReader.

How to deal with several DataReaders in a Participant matching the same DataWriter ? Most of the time, the submessage destination is ENTITY_UNKOWN. As a consequence a clarification is required.