The value of the identity information for a Group Member with
its type indicated by the cgmGdoiGmIdType. Use the
cgmGdoiGmIdType to parse the Group Member ID correctly.
This Group Member ID value is sent as the 'SRC
Identification Data' and 'DST Identification Data' of the
KEK and TEK payloads for GDOI GROUPKEY-PULL and GROUPKEY-PUSH
exchanges.