The value of the Security Parameter Index (SPI) of a KEK
SA. The SPI must be the ISAKMP Header cookie pair
where the first 8 octets become the 'Initiator Cookie' field
of the GROUPKEY-PUSH message ISAKMP HDR, and the second 8
octets become the 'Responder Cookie' in the same HDR. As
described above, these cookies are assigned by the GCKS.