PQ/Hybrid Transport Protocol

Abstract

This LP defines post-quantum secure transport layer protocols for all LuxDA Bus network communications.

Motivation

Transport layer security is the first line of defense against network attackers. This LP ensures:

1. Forward secrecy against future quantum adversaries
2. Authentication of all network peers
3. Seamless upgrade from classical to hybrid to PQ-only

Specification

1. Protocol Stack

┌─────────────────────────────────────┐
│         Application Layer           │
├─────────────────────────────────────┤
│      LuxDA Bus Protocols            │
├─────────────────────────────────────┤
│      PQ-Noise Framework             │
├─────────────────────────────────────┤
│      QUIC / TCP                     │
└─────────────────────────────────────┘

2. PQ-Noise Handshake

Based on Noise NK pattern with X-Wing KEM:

→ e
← e, ee, ekem, s, es
→ s, se, skem

type PQNoiseHandshake struct {
    // Initiator ephemeral
    EphemeralKEM    *XWingKeyPair
    EphemeralDH     *X25519KeyPair

    // Static keys
    LocalStatic     *XWingKeyPair
    RemoteStatic    *XWingPublicKey

    // Derived secrets
    ChainingKey     [32]byte
    HandshakeHash   [32]byte
}

func (h *PQNoiseHandshake) Initialize(prologue []byte)
func (h *PQNoiseHandshake) WriteMessage(payload []byte) []byte
func (h *PQNoiseHandshake) ReadMessage(message []byte) []byte
func (h *PQNoiseHandshake) Split() (CipherState, CipherState)

3. Key Derivation

// Combined KDF using HKDF-SHA256
func CombineSecrets(
    dhSecret []byte,     // X25519 shared secret
    kemSecret []byte,    // ML-KEM shared secret
) []byte {
    return hkdf.Extract(sha256.New,
        append(dhSecret, kemSecret...),
        []byte("LuxPQNoise"))
}

4. Cipher Suite

type CipherSuite struct {
    KEM       string  // "X-Wing"
    Cipher    string  // "ChaChaPoly"
    Hash      string  // "SHA256"
}

var DefaultSuite = CipherSuite{
    KEM:    "X-Wing",
    Cipher: "ChaChaPoly",
    Hash:   "SHA256",
}

5. Connection Establishment

type SecureConn interface {
    // Handshake performs PQ-Noise handshake
    Handshake(ctx context.Context) error

    // RemotePeer returns authenticated peer identity
    RemotePeer() PeerID

    // Read/Write encrypted data
    Read(b []byte) (int, error)
    Write(b []byte) (int, error)

    // Close with graceful shutdown
    Close() error
}

// Upgrade raw connection to secure
func UpgradeOutbound(
    ctx context.Context,
    conn net.Conn,
    localKey *XWingKeyPair,
    remotePubKey *XWingPublicKey,
) (SecureConn, error)

func UpgradeInbound(
    ctx context.Context,
    conn net.Conn,
    localKey *XWingKeyPair,
) (SecureConn, error)

6. Session Resumption

type SessionTicket struct {
    TicketID      [16]byte
    CreatedAt     uint64
    ExpiresAt     uint64
    ResumptionKey [32]byte  // Encrypted with server key
}

// 0-RTT resumption with forward secrecy
func ResumeSession(ticket SessionTicket) (SecureConn, error)

7. Peer Authentication

type PeerIdentity struct {
    PublicKey     *XWingPublicKey
    Certificate   *PeerCertificate  // Optional
    AttestationChain []Attestation  // Optional (for validators)
}

type PeerCertificate struct {
    Subject       PeerID
    PublicKey     *XWingPublicKey
    ValidFrom     uint64
    ValidUntil    uint64
    Issuer        PeerID
    Signature     []byte  // ML-DSA signature
}

8. Wire Format

Handshake Message Format:
┌────────────────────────────────────────────┐
│ Version (1 byte)                           │
├────────────────────────────────────────────┤
│ Message Type (1 byte)                      │
├────────────────────────────────────────────┤
│ Length (2 bytes, big-endian)               │
├────────────────────────────────────────────┤
│ Payload (variable)                         │
│   - Ephemeral public key (1216 bytes)      │
│   - KEM ciphertext (1120 bytes)            │
│   - Encrypted payload                      │
└────────────────────────────────────────────┘

9. Migration Support

type TransportVersion int

const (
    TransportClassical TransportVersion = 1  // X25519 only
    TransportHybrid    TransportVersion = 2  // X-Wing (X25519 + ML-KEM)
    TransportPQOnly    TransportVersion = 3  // ML-KEM-1024 only
)

// Version negotiation
func NegotiateVersion(local, remote []TransportVersion) TransportVersion

Security Considerations

1. Forward secrecy: Ephemeral keys ensure past sessions remain secure
2. Hybrid security: X-Wing combines classical and PQ security
3. Authentication: Peer identity bound to handshake transcript
4. Replay protection: Nonces and session IDs prevent replay attacks

Test Plan

1. Handshake interoperability with reference implementation
2. Performance benchmarks (latency, throughput)
3. Stress testing under high connection rates
4. Migration path testing (v1 → v2 → v3)

References

• Noise Protocol Framework
• X-Wing IETF Draft
• LP-2200: PQ Crypto SDK

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LP-2210 v1.0.0 - 2026-01-02