Announce

An announce broadcasts a destination's keys so peers can address and route to it. This section is proven by [VEC-ANN-NORATCHET] and [VEC-ANN-RATCHET].

Packet

An announce is an ANNOUNCE-type packet (packet_type = 0x01) to the announced SINGLE destination. The context flag (header bit 5) is set when a ratchet is included (Destination.py:310-311). [VEC-ANN-NORATCHET] flags byte 01 (ANNOUNCE, context flag 0); [VEC-ANN-RATCHET] flags byte with context flag 1.

Announce data layout

The packet data is (Destination.py:301):

public_key(64) || name_hash(10) || random_hash(10) || [ratchet(32)] || signature(64) || app_data

The ratchet field is present only when the context flag is set. Without it the data is 64 + 10 + 10 + 64 = 148 bytes plus app_data; with it, 180 plus app_data. [VEC-ANN-NORATCHET] carries 150 data bytes (148 + 2-byte app_data); [VEC-ANN-RATCHET] carries 182 (180 + 2).

The random_hash is get_random_hash()[0:5] || int(time.time()).to_bytes(5, "big") (Destination.py:282): 5 random bytes and a 5-byte big-endian Unix timestamp. It makes each announce unique and lets receivers reject replays.

Signed data

The signature covers (Destination.py:297-300):

signature = sign( destination_hash || public_key || name_hash || random_hash || [ratchet] || app_data )

The destination hash is signed but not transmitted in the announce data; the receiver recomputes it from the transmitted keys (below). This binds the keys to the address without spending 16 bytes on the wire.

Validation

A receiver validates an announce by (Identity.py:568-670):

parsing public_key = data[:64], then name_hash, random_hash, optional ratchet (when the context flag is set), signature, and app_data at the offsets above (Identity.py:582-600);
reconstructing signed_data and verifying the signature against the transmitted public key (Identity.py:579);
recomputing expected_destination_hash = truncated_hash(name_hash || identity_hash) and checking it matches (Identity.py:584-585);
remembering the public key, app_data, and (if present) the ratchet for future encryption (Identity.py:634,654-655).

[VEC-ANN-NORATCHET] and [VEC-ANN-RATCHET] are frozen-injection vectors: under pinned randomness and time the announce reproduces byte for byte, and the genuine validate_announce returns true. An implementation MUST reproduce the signed-data order and the destination-hash recomputation, or a Python peer rejects the announce.

Path response