Final Network Protocol

FNP in the documentation: the suite it speaks, a session from handshake to rotation and failover, pinning, and where it runs today, at release and on Final Chain.

Last updated 2026-09-05 · maintained in the Final Wiki

FNP: the session-multiplexed, post-quantum tunnel protocol our nodes speak.

#What it is

The Final Network Protocol replaces TLS on every path where the protocol talks to itself or to a wallet. One authenticated session carries many tunnels at once, rotates its keys with zero downtime, and gives perfect forward secrecy by construction: a key that is compromised later opens nothing that was sent before. It is written in C and C++, runs its cryptographic core in constant time, and has been in production inside Final DeFi since 2024.

#The suite

Purpose	Algorithms	Note
Key establishment	ML-KEM-1024 (FIPS 203), HQC-5 (NIST selection 2025), Classic McEliece-8192128, FrodoKEM-1344	All four are used in every handshake; the session key is derived from all four shared secrets, so it stands while any one of them stands
Authentication	ML-DSA-87 (FIPS 204), SLH-DSA-SHAKE-256s (FIPS 205) and FN-DSA-1024 (FIPS 206), over the endpoint identity certificates	Both endpoints present Final Certificates; every signature the certificate carries must verify. Which algorithms a certificate carries is configurable per certificate, so the set an endpoint authenticates with is the set its certificate declares
Content	Four nested authenticated layers: AES-256-GCM innermost, then ARIA-256-GCM, then Camellia-256-GCM, XChaCha20-Poly1305 outermost — four independent keys, the frame header authenticated by every layer, one 16-byte tag per layer	The same encapsulation the intent envelope uses (AES-256-GCM inside XChaCha20-Poly1305), taken to four layers; a joint key search stays at 2^512 under Grover's algorithm
Hashing and derivation	SHA3-256 (FIPS 202), SHAKE	Every digest and every derived key

Plainly: four different locks agree on the session key, so it holds while any one of them holds; both sides prove who they are with their certificates; the content travels under four ciphers with four separate keys, each sealing the last; and every digest is SHA3.

The four key-encapsulation families are fixed for the handshake; the signature set follows the certificates. Algorithms are identified by registry id, and the registry is widening: many more post-quantum algorithms become configurable per certificate soon, so what one endpoint chooses is whatever its certificate carries. The same algorithms appear across the Final Chain nodes; see Post-quantum cryptography and Final Certificates.

#A session

Handshake. Client and server exchange hello messages under a 20-byte handshake header, prove their identities with their Final Certificates and establish the session key from all four encapsulations. Timestamps and nonces refuse replays.
Data transfer. Once the session is up, packets carry a 6-byte header, or 11 bytes with reliability enabled, and counter-based nonces that are never sent on the wire: 70 bytes of overhead per frame (the header and the four 16-byte tags), 75 with acknowledgements.
Tunnels inside the connection. Many logical tunnels share one session and one connection, so a new stream costs no handshake.
Rotation without downtime. Session keys rotate on a configurable interval (ten seconds is typical). Traffic migrates from the old session to the new one gradually and probabilistically over that interval, with no interruption and no packet loss; the old key material is overwritten and released.
Reliability and failover. An optional acknowledgement protocol guarantees delivery where a service needs it; missed acknowledgements trigger graceful degradation to a standby session and an event for investigation.

#Pinning

Endpoints authenticate with certificates of the network-authentication purpose; hosts and agents pin the identities they expect, so a substituted endpoint is refused even with a valid certificate of its own. Because the chain is the only root, there is no certificate store to poison and no self-signed anchor to install.

#Where it runs

Today: between the protocol's own services and nodes — internal and external communications alike.
With the release: post-quantum tunnels from Final Wallet to our nodes, certificate-authenticated and key-encapsulated, terminating at the node rather than at a TLS edge.
On Final Chain: the node-facing encrypted tunnel becomes a node module, and the Final Node agents gain a management plane — central configuration and updates, coordinated NAT traversal for direct connections between agents, aggregate metrics, role-based administration. That plane is future work; the protocol it manages is the one described here.