5.1 Security Considerations for Implementers
The RDP multitransport connections use SSL and DTLS, respectively, for reliable and unreliable UDP transport connections for data encryption and server certificate validation.
The client is authenticated to the server by presenting a security cookie as part of the Tunnel Create Request PDU (section 2.2.2), which the server provided to the client over the secure main RDP connection, as defined in [MS-RDPBCGR].