Nokia University of the Bundeswehr Munich This document defines a binary, application-layer transport protocol for exchanging Exported Authenticator messages between two peers over TLS. It provides the signaling required to initiate and complete post-handshake authentication exchanges at the application layer, without requiring modifications to the TLS layer itself. While primarily intended to support attestation exchange, the transport is generic and can be used independently for any Exported Authenticator exchange. The document further specifies how protocol messages are conveyed as Capsules over an HTTP connection established using the Extended CONNECT method, with support for both HTTP/2 and HTTP/3. In addition, it defines how the protocol can operate directly over TLS or DTLS 1.3 without an HTTP binding, using a so-called "Shim Mode".