The ECDH Protocol Discipline Trap

Amid the ubiquitous deployment of Deep Packet Inspection (DPI) systems capable of active probing, traditional methods for securing consensus-based P2P networks rely heavily on cryptographic tunneling (e.g., ECDH). This paper demonstrates a fundamental vulnerability in this approach, rooted not in cryptographic primitives, but in the interactive state machine discipline of key exchange protocols themselves. We prove that the state machine of any interactive protocol inherently forces a node to respond to blind probing, inevitably deanonymizing hidden metadata (such as node identifiers). We formalize an impossibility theorem proving that in-band authentication and steganographic obfuscation are mutually exclusive. As a solution, we introduce Stateless Steganography, leveraging native cryptographic point obfuscation and a strict ``Silent Drop'' policy, preserving perfect steganographic deniability without compromising authentication.