HTT Consulting AX Enterprize Linköping University Aircraft-to-anything (A2X) communications are often single broadcast messages that need to be signed with expensive (in cpu and payload size) asymmetric cryptography. There are also frequent cases of extended exchanges between two devices where a lower cost symmetric key protect flow can be used. This document shows both how to secure A2X broadcast messages with DRIP DET and Endorsement objects and to leverage these to create an AdHoc session key for just such a communication flow.