Knit 2.3.0-alpha.0 (pre-release)

Forward secrecy for direct messages and group chats, encrypted delivery receipts and reactions, and
optional Internet relays for when nobody is in radio range.

Added

• Direct messages between updated phones are now forward-secret. Each conversation derives its own key
  material from a prekey published in your profile, then re-keys as the conversation goes back and
  forth, and drops the old keys. Someone who records traffic today and gets hold of a phone later
  cannot read the earlier messages.
• Group chats gain the same property. Every member drives their own key chain and hands its current
  seed to the others inside encrypted direct messages. A group's info screen says whether the group is
  running the new scheme or still waiting on somebody to update.
• Delivery receipts and reactions are encrypted. Until now they crossed the mesh readable by any phone
  relaying them, so an onlooker could tell when a message reached you, and who reacted to which
  message with what. They now travel sealed and look like ordinary messages on the wire.
• Knit can now use Internet relays, which you turn on yourself. Knit remains a messenger that works
  with no internet and no account, but a message to somebody out of radio range used to wait for the
  two phones, or a chain of phones between them, to meet. With relays on, Knit parks a sealed copy on
  a relay server, which hands it over the next time the other phone connects. A one-time explanation
  spells out what a relay can see — your IP address, when you send, and roughly how much — and what it
  cannot: your messages or photos, who you are talking to, or who else is in a group.
• A Settings screen for relays lists the ones you use, adds and removes them, and reports each one as
  connected, still connecting, or why it refused. Knit ships with one relay already listed and unused;
  it stays inert until you turn the feature on, and removing it sticks.
• Group chats travel over relays as well as direct messages, without anyone learning from the relay
  that a group exists or who is in it.
• Photos travel over relays too, in sealed pieces. A photo waits while a phone that can carry it is
  still in radio range, so an ordinary in-person exchange never touches a relay. Where a relay cannot
  take it — no photo support, or the photo is larger than any relay in your list will hold — the
  message says "Nearby only" rather than reporting a failure: it still arrives over Wi-Fi or Bluetooth
  as it always did.
• Changes to your name, status, or photo now reach people you have only ever met across a relay. They
  previously spread by radio alone, so such a contact kept whatever it saw when you were last in
  range.
• A conversation says how it is being carried. A globe appears beside the double tick when the other
  phone answered over the internet, and beside a message that arrived that way; the connection header
  says when the radios are dark and a relay is carrying the conversation. The Nearby room is exempt by
  design — it is public and unencrypted, so it is never uploaded, and says so.
• Diagnostics gains an Internet relays section: what has been sent and received over them, photo
  pieces moved, photos left to the radios, and any errors a relay reported.

Changed

• Chats with a phone on an older version keep working, on the previous encryption scheme. A group
  falls back the same way while any one member has not updated, and moves over on its own once
  everyone has.
• The Profile entry in the overflow menu is now called Settings, since the screen also holds settings
  that are not about you, such as content filtering and the relay switch.

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Pre-release — a test build, not a shipping release. It is not on F-Droid, is not marked
Latest, and is not what F-Droid's Binaries: URL points at. Install it only if you mean to
test it.

knit-2.3.0-alpha.0.apk — sha256:e99993a33b73fd06480828365ac5f82fe7142c00786394543295dd01f8a1279c

Signed with Knit's distribution key (certificate b18a283d11797c2a84a008c1fcb9e1b864e7b4c3b301408f7a4a80624b0e631c) — the same key every off-Play Knit
build carries — so it installs straight over an existing F-Droid, GitHub or mesh-shared install
without an uninstall, and keeps your messages.

Going back to the current stable is not possible in place: Android refuses the versionCode
downgrade, so reverting costs an uninstall and everything stored on the device with it. The next
stable release will update over this build normally.

CI verified this APK is byte-identical, apart from the signature, to an independent unsigned
rebuild produced inside F-Droid's own buildserver image — the same reproducibility gate stable
releases pass.

mapping-2.3.0-alpha.0.txt.gz is the R8 deobfuscation map for symbolicating crash reports from this build.