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jackandClaude Opus 5
10f1e5c8b7
Code is a better thing to argue with than prose, so the spec now has a working, tested base under it. Every number and context string is a concrete proposal you can reject by changing one function and watching a test vector move. What is implemented: - PeerIDRotation: hour epochs with a ±1 matching window, the rotation secret from the Noise static *private* key, per-epoch peer IDs, pairwise recognition keys and tags from an X25519 shared secret, the fixed-width tag block with CSPRNG padding and constant-time matching, and the canonical bytes for the identity binding. - AnnounceV2Packet (announceV2 = 0x05): TLV wire format carrying an epoch, a 64-byte tag block, capabilities and an optional bridge cell — and nothing else. No nickname, no public keys, no neighbour list. Rejects a wrong-width tag block on both encode and decode, since a short block would disclose how many mutual favourites someone has, and rejects non-canonical capability encodings the way AuthenticatedPeerStatePacket does. Unknown TLVs are skipped for forward compatibility. - 37 tests, three of which are hex vectors cross-checked against an independent implementation written from the spec alone (Python hmac/hashlib, HKDF extract-then-expand, empty salt) and matching byte for byte. That is the property Android needs: the document is sufficient to reproduce the numbers without reading this code. What is deliberately NOT implemented: nothing emits a v2 announce, and BLEService parses the type and explicitly ignores it. Consuming presence needs both the replacement identity binding and a decision on how unverified presence appears in the peer list, and accepting it now would put unauthenticated entries in front of people. Adding the message type forced three policy decisions, all reviewable: - Not gossip-synced. Syncing presence would defeat the point — a device never in radio range could collect tag blocks, turning a local beacon into a network-wide one. - Not padded. At ~75 bytes the smallest bucket would triple the airtime of the most frequent packet in the protocol; the format is already near-constant width, and fixing the capability and geohash field widths would be cheaper than padding. - Parsed but ignored on receive, as above. Notably the v2 announce is *smaller* than v1 (~75 vs ~229 bytes): dropping two 32-byte keys, the neighbour list and the signature more than pays for 64 bytes of tags, so unlinkability here costs less airtime rather than more. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>