Crate zerodds_security_keyexchange 

Crate zerodds-security-keyexchange. Safety classification: SAFE (a thin wrapper around ring::agreement + ring::hkdf).

X25519 / P-256 ephemeral Diffie-Hellman for the DDS-Security 1.1 authentication handshake (spec §8.3.2).

Layer position

Layer 4 — Core Services. Consumed by zerodds-security-pki.

Purpose

The Authentication handshake (spec §8.3.2) needs a SharedSecret at the end. The usual way is ephemeral DH: each side generates a temporary key pair, exchanges the public keys, and derives the shared secret from x25519(priv, remote_pub). HKDF-SHA256 pulls a 32-byte key from it.

API

use zerodds_security_keyexchange::KeyExchange;

// Both sides generate ephemerals.
let alice = KeyExchange::new().expect("alice");
let bob = KeyExchange::new().expect("bob");

// Exchange public keys (via the SPDP handshake token).
let a_pub = alice.public_key().to_vec();
let b_pub = bob.public_key().to_vec();

// Each side derives the same 32-byte SharedSecret.
let s1 = alice.derive_shared_secret(&b_pub).expect("alice derive");
let s2 = bob.derive_shared_secret(&a_pub).expect("bob derive");
assert_eq!(s1, s2);

Public API (as of 1.0.0-rc.1)

• KeyExchange + KxSuite::X25519 / KxSuite::EcdhP256 — ephemeral-DH roundtrip with deterministic SharedSecret derivation.

Non-goals

RSA-OAEP key transport (spec §8.3.2.11 as an optional alternative for legacy vendors without ECDH/X25519) is explicitly not in RC1: all relevant vendors (Cyclone DDS, FastDDS, RTI Connext) speak ECDH or X25519, and ring 0.17 exposes no RSA encrypt API. If a concrete legacy use case appears, the path via the rsa crate is reintroduced as a major-2.0 additive extension.

Structs

KeyExchange

Ephemeral DH key pair for a single handshake.

Enums

KxSuite

DH suite selection.