LMXF-specification/Codex_Response_1.md

No, I don’t need SPEC.md or SOURCES.md for this first report. I used the checked-out LXMF source directly. I did not edit SPEC.md or any other file.

LXMessage Serialized Structure

Source inspected: LXMF commit fab12ad9bf9f997797034950f289fe41a79dcf5a

Core lxmf_bytes layout:

destination_hash || source_hash || signature || msgpack_payload

Where msgpack_payload is:

[
  timestamp,
  title,
  content,
  fields,
  optional_stamp
]

The fifth element is only present when a normal message stamp is generated and appended.

Field	Serialized position	Type / size	Source origin	Test vector confirmed
destination_hash	bytes 0..15	16 bytes	LXMessage.py, length from LXMessage.py and RNS 128-bit truncated hashes in Reticulum.py	No
source_hash	bytes 16..31	16 bytes	LXMessage.py	No
signature	bytes 32..95	64 bytes	LXMessage.py, LXMessage.py; RNS signature length from Identity.py and Identity.py	No
msgpack_payload	bytes 96..end	msgpack list	LXMessage.py, packed at LXMessage.py	No
timestamp	payload index 0	Python float, normally msgpack float64 on this RNS umsgpack	LXMessage.py, LXMessage.py; float64 behavior from umsgpack.py and umsgpack.py	No
title	payload index 1	bytes	LXMessage.py, LXMessage.py, LXMessage.py	No
content	payload index 2	bytes	LXMessage.py, LXMessage.py, LXMessage.py	No
fields	payload index 3	dict, default {}	LXMessage.py, LXMessage.py	No
stamp	payload index 4, optional	bytes, only if generated	LXMessage.py, LXMessage.py; extracted on unpack at LXMessage.py	No

Hash And Signature

message_id / hash is:

SHA256(destination_hash || source_hash || msgpack([timestamp, title, content, fields]))

Source: LXMessage.py, LXMessage.py, RNS SHA-256 at Identity.py.

The signature is over:

destination_hash || source_hash || msgpack([timestamp, title, content, fields]) || message_id

Source: LXMessage.py, LXMessage.py, RNS signing at Identity.py.

Important: the optional normal stamp is excluded from both message_id and signature. Unpack removes payload index 4 before recomputing hash/signature material: LXMessage.py.

Outer Representations

Direct/link/resource delivery uses full self.packed unchanged: LXMessage.py, LXMessage.py.

Opportunistic packet delivery omits the destination hash from the packet payload because the RNS packet destination already implies it:

source_hash || signature || msgpack_payload

Source: LXMessage.py.

Propagated and paper messages wrap/encrypt everything after the destination hash:

destination_hash || encrypted(source_hash || signature || msgpack_payload)

Source: propagated LXMessage.py, paper LXMessage.py. Propagation transit additionally msgpacks [time.time(), [lxmf_data]]: LXMessage.py.

Notes

The README is not authoritative here: it describes payload order as timestamp, content, title, fields, but current code serializes timestamp, title, content, fields.

No test vector confirmation exists in this checkout. There is no tools/ directory and no tracked SPEC.md or SOURCES.md, so every “Test vector confirmed” entry above is marked No.