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Examples

These examples are designed to be read alongside MAIN.md.

Example 1 — First contact handshake (high level)

Inputs (out-of-band)

Alice obtains an introduction token for Bob. Conceptually, it contains:

  • Bob’s identity public keys (Ed25519 + Dilithium)
  • Bob’s operational signing key (MTSK)
  • Bob’s prekey encryption public keys (X25519 + Kyber768)
  • A temporary DHT address and expiration
  • Bob’s signature over the token contents

Step A — Alice constructs ClientHello

Illustrative structure:

ClientHello
  protocol_version = 1
  alice_ltik_pub = (ed25519_pub, dilithium_pub)
  alice_mtsk_pub = ed25519_pub
  alice_ephemeral_x25519 = x25519_pub
  alice_kem_kyber_pub = kyber768_pub
  kyber_ciphertext_to_bob = Kyber768.Encapsulate(bob_kyber768_pub).ciphertext
  supported_ciphers = [ChaCha20-Poly1305, AES-256-GCM]
  timestamp = unix_time_ns
  signatures = Sign_ed25519(...) + Sign_dilithium(...)

Alice then encrypts and routes this first contact through the mesh.

Step B — Bob validates and responds with ServerHello

Illustrative structure:

ServerHello
  bob_ephemeral_x25519 = x25519_pub
  kyber_ciphertext_to_alice = Kyber768.Encapsulate(alice_kem_kyber_pub).ciphertext
  selected_cipher = ChaCha20-Poly1305
  timestamp = unix_time_ns
  signatures = Sign_ed25519(...) + Sign_dilithium(...)

Step C — Both derive a shared secret and initialize the ratchet

Conceptually:

SS = HKDF( X25519_shared || Kyber_shared_ab || Kyber_shared_ba, context="LMP-v1-session-init" )
RK_0 = HKDF( SS, context="LMP-ratchet-root" )

Example 2 — One message send

Header fields (illustrative)

Header
  conversation_id
  sender_device_id
  message_number
  prev_chain_length
  timestamp
  (optional) new ratchet public keys

Nonce derivation (illustrative)

nonce_prefix = HKDF(conversation_id || sender_device_id, "LMP-nonce-prefix")[0..4]
nonce = nonce_prefix || little_endian_u64(message_number)

Encrypt

ciphertext, tag = AEAD_Encrypt(
  key = MK_send,
  nonce = nonce,
  plaintext = message,
  associated_data = header
)

Notes

  • The examples here are meant to reduce ambiguity while reading the main spec.
  • If any example conflicts with MAIN.md, treat MAIN.md as authoritative.