5 Commits

Include renames

Author	SHA1	Message	Date
jackandClaude Opus 5	4158d5fca3	Close the review findings on the rotation spec ... **P1 — the binding proof was replayable onto another session.** The §4.5 verifier checklist omitted the check that the proof's noiseStaticPublicKey equals the remote static key the Noise session actually established. The proof is a self-contained signed blob with nothing tying it to the session it arrives on, so a peer M that had seen A's proof could replay it verbatim inside M's own session with B; B would verify A's signature, see a well-formed binding, and on first contact TOFU-pin A's signing key against M's fingerprint. Added as the first item in the checklist, with the attack written out, because "signed" and "bound to this conversation" are different properties and the difference is easy to lose in a bullet list. **announceV2 is 0x2C, not 0x05.** 0x05 only looks free. It has been recycled twice — announce, then bulkTransferResponse, then fragmentStart until #446 — so an old peer could still map it to a fragment header and misparse presence as a partial message. Values above voiceFrame = 0x29 have only ever been allocated forward, and 0x2A/0x2B belong to the courier spray-ack work, leaving 0x2C. Confirmed never used anywhere in this repository's history. **Outbound priority is now stated, not inherited.** announceV2 fell through to `default: .high`. High is the right answer — presence is small, time-bounded to its epoch and useless once stale — but for a type nothing emits yet, a fall-through means the choice gets made without anyone seeing it. **Reverted unexplained pbxproj churn.** Xcode had rewritten resource-phase ordering and dropped a share-extension entitlements membership exception; none of it belongs in this PR. The file now matches main byte for byte. **O7 said "payloads" where the arithmetic is over encoded frames.** The 241-256 / 497-768 / 1009-1792 ranges are what `pad` receives, which is the whole encoded packet, not the payload alone. **Added O9: a seized device recomputes every past peer ID.** K_rot is long-lived, so peerID_e is computable for any epoch by whoever holds it — someone who seizes a phone, or pulls the static key from a backup, can go back over historical radio captures and identify which were this device. Rotation defends against the passive observer, not against later key compromise. A hash ratchet would give forward secrecy for the ID stream at the cost of state that must survive restarts, tolerate clock jumps, and resynchronise after a gap — a real trade rather than an obvious win, so it is written down as a question rather than silently adopted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-07-26 22:41:31 +01:00
jackandClaude Opus 5	574912670f	docs: record that padding changes are cross-platform coordinated ... O7 began as a question about whether Android tolerates trailing bytes. The firmer answer, found while attempting the padding fix unilaterally: toBinaryDataForSigning encodes with padding enabled, so the padding bytes are inside the signed material for every signed packet. Changing the algorithm changes the signed byte stream and breaks verification against any peer that has not made the identical change. So both outstanding padding fixes — coverage beyond Noise frames, and the gap where a frame needing over 255 bytes of padding ships unpadded — are wire changes requiring both platforms, not local cleanups. O7 now says so, and names the two things to settle. Also updates the related-work section: dropping the neighbour list and randomizing origin TTL did turn out to be unilateral and have landed separately. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-07-26 21:04:26 +02:00
jackandClaude Opus 5	c9f2f418ca	Fix two P1 flaws in the recognition tag design (Codex #1487) ... Both findings are correct and both were real. This is the argument for shipping code next to the prose: neither was obvious in the design text. **Tags were symmetric, which leaked the social graph.** `HMAC(K_AB, epoch)` produces the same 8 bytes for both parties, so an observer who saw one value in two different announces would learn those two devices are mutual favourites, and could link their two rotating IDs to each other — handing over exactly the graph the design exists to hide, plus a cross-epoch correlation handle. Tags are now directional: the MAC covers the ordered sender and recipient static public keys, so A→B and B→A differ. Both parties can still compute both directions because both hold both keys. **Tags were replayable under any ID.** A tag depending only on (pair, epoch) could be lifted from a recorded announce and replayed in a fresh announce under an attacker-chosen ID; the recipient would match and treat that ID as the favourite, and since epoch-1 is accepted it would keep working into the next period. The MAC now covers the announced peer ID, which reduces this to replaying the victim's own presence. That residual is unfixable while announces are unsigned, so the spec now states plainly that recognition is a hint only: presence may be populated, but routing a DM or showing a verified badge must wait for a handshake whose static key equals the favourite that produced the match. O4 is rewritten around that, with the two alternatives named (per-epoch ephemeral signing key, or a freshness nonce echoed by the recipient). Tests: two regression cases named for the findings, plus a wrong-direction-does-not-match case so the directional fix cannot silently become cosmetic. The vector table now gives both directions, because their difference is the security property — an implementation that produces one value for both has reintroduced the flaw. Recomputed independently in Python from the spec and matched byte for byte. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-07-26 20:49:10 +02:00
jackandClaude Opus 5	10f1e5c8b7	Implement the peer ID rotation primitives ... 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>	2026-07-26 19:54:34 +02:00
jackandClaude Opus 5	19a56780d0	docs: specify peer ID rotation for cross-platform review ... Draft protocol spec for review by both iOS and Android before any implementation. Nothing here is implemented; this is the artifact to agree on, since the change is a wire revision neither platform can ship alone. The headline correction, because it is easy to get wrong: rotating the peer ID alone accomplishes nothing. The announce carries the Noise static key, the Ed25519 signing key and the nickname in cleartext, so a rotated ID is re-linked to the same device on its first announce. Rotation and announce confidentiality have to land together. The second thing an implementer needs to know up front is that peerID == SHA-256(noiseStaticKey)[0..8] is not a convention, it is the mechanism that makes peer IDs unforgeable, enforced in the announce preflight and again at handshake completion. Making IDs independent of the key fails both checks for every peer, so a replacement binding has to ship in the same change. The spec proposes one: an Ed25519 proof over (context, epoch, rotating ID, static key) carried inside the completed Noise session via the existing AuthenticatedPeerStatePacket, checked against a pinned signing key — strictly stronger than today's self-signed announce. Design summary: hour-epoch IDs derived from private key material via HKDF+HMAC so no observer can predict or link them; pairwise recognition tags from the X25519 shared secret so mutual favourites still recognise each other with no handshake, padded to fixed slots so the tag count does not leak how many favourites someone has; strangers discovered by handshake-first-identify-second over Noise XX, whose static keys are already encrypted on the wire. Nickname moves inside the session and the neighbour list is dropped rather than rotated. Includes a verified impact inventory separating what breaks hard (the handshake check, the announce preflight, the disk outbox keyed by peer ID, private-media stable IDs and their deletion tombstones, the initiator tie-break, fingerprint-prefix lookups) from what degrades gracefully and what is already safe because it keys on fingerprints or Noise keys. Rollout uses the two mechanisms already proven in this repo: a PeerCapabilities bit (11 is next; 10 is burned) with capabilitiesWereExplicitlyAdvertised to tell an old client from a new one with the bit off, and observed-version gating as used for source routing. Two findings surfaced while writing this and are recorded in the spec. CourierEnvelope.recipientTag is HMAC keyed on the recipient's *public* static key, and since that key is broadcast in cleartext today, any observer in radio range can compute a peer's courier tags for any day — so the whitepaper's "cannot link it across days" does not currently hold, and the pattern must not be copied. And NoiseEncryptionService's buildAnnounceSignature/verifyAnnounceSignature/canonicalAnnounceBytes are present but production-dead, called only from tests; the binding above deliberately uses a different context string so the two can never be confused. Eight open questions are left explicitly unresolved, including the rotation period, whether unsigned v2 announces are an acceptable posture, and whether Android's decoder tolerates trailing bytes the way iOS's does (which decides whether padding coverage can ship ungated). Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>	2026-07-26 19:33:56 +02:00