Paul HittandClaude Opus 5
44e06adf92
256/256 private keys now produce lyrebird's exact public key, and the whole keypair -- private key to public key and representative -- matches end to end. 13 tests. BouncyCastle's X25519.scalarMult cannot be used for this: it clamps internally and runs 255 bits, while the dirty variant needs the COMBINED scalar fed to a 256-bit ladder with no re-clamping. The combined scalar can exceed 2^255 once lsb*L is added, so a 255-bit ladder silently drops the top bit for a fraction of keys. Only the ladder and the scalar handling are written out; the field arithmetic underneath is still BouncyCastle's. The danger here is that the wrong answer looks entirely fine. A clean X25519 public key agrees on shared secrets and round-trips; it is just confined to the prime-order subgroup and therefore distinguishable, and clamping the private key before the call is all it takes to get one. So there is a structural test beside the byte comparison: the dirty key must differ from the clean key exactly when the low three bits of the private key are non-zero, with both arms asserted to actually occur so neither passes vacuously. cswap here uses an explicit mask rather than any BouncyCastle conditional. Nothing in this module assumes those take a boolean-shaped condition, after X25519Field.cmov was found to do nothing at all when handed a plain 1. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Flamenet Messenger — Android
The Android app, and the two libraries under it.
engine/ the protocol: X3DH, Double Ratchet, sealed sender, safety numbers,
key transparency. Plain Kotlin/JVM — no Android in it at all.
client/ the relay transport: HTTP, auth, the §8 routes.
app/ the Compose app.
interop/ the cross-engine driver; not shipped.
engine and client are deliberately plain JVM libraries. The protocol has
nothing to do with Android, and keeping it off the platform means their tests
run anywhere a JVM does — no SDK, no emulator, no device, which is also what
lets them gate in CI on Linux:
./gradlew :engine:test :client:test
The app's own unit tests need the Android SDK but still no emulator (Robolectric):
./gradlew :app:testDebugUnitTest
Where it stands
PARITY.md is the definition of done for this app — read that, not this. Every row there names the iOS file it came from so it can be re-checked rather than trusted. Headlines as of 2026-08-28: messaging, groups, attachments, voice notes, stories, calls, sealed sender, key transparency and the encrypted vault are built and tested; a cross-platform round trip against iOS was verified on 2026-08-26.
⚠️ This file said "Nothing here is an app yet" until 2026-08-28, above a tree containing the finished app — the README described the repository as it was when the engine landed and nothing updated it as the app grew around it. If a claim here ever disagrees with PARITY.md or with the tree, believe those, and fix this.
Why the engine came first, and is held to the vectors
An Android client needs the protocol implemented a third time, and the third
implementation is the one that finds the places where the specification says
less than the two existing engines quietly agreed on — but only if it is
written against the spec and the published vectors rather than against a
reading of our own Swift and JavaScript. So the engine is held to
test/vectors/protocol-v1.json in
flamenet-e2e — the same file the
other two engines are checked against, read from that repository rather than
copied here, because a copied vector file drifts and a drifting vector file
stops being a check. PublishedVectorsTest looks for it beside this checkout
and fails loudly if it cannot find it; FLAMENET_VECTORS overrides the search.
Two implementations that agree may both be wrong in the same way, especially when one was written while reading the other. The audit-path ordering in §19 is the worked example: a top-down reading of a bottom-up path produces the correct root for every left-spine index, so it passes any test that only checks index 0. The vector file pins a right-descending index for that reason, and the Kotlin tests assert both that the published path verifies and that the same path reversed does not.
If this engine ever disagrees with the file, the interesting question is which of the three is wrong — not this one by default.
Contributing and security
- CONTRIBUTING.md — building (JDK 21,
JAVA_HOMEis not optional on a Mac), the test gate, and the platform traps that cost an hour each. - PARITY.md — what iOS does, what this does, and what is left. It is the definition of done for this app.
- SECURITY.md — threat model and where to send a vulnerability report. Not an issue tracker matter: security@flamenetmessenger.com.