a0b7985cbe
* Cohere per-link Noise auth and rebind containment into BLELinkAuthState The authenticated-link owners, the reconnect revalidation policy, and the two rebind-containment cooldowns were four loose bleQueue-owned maps whose invariants lived in call-site discipline: every teardown path had to remember to retire the proof AND close the revalidation epoch (the pair appeared seven times), and both cooldowns hand-rolled the same prune-check-record dance. BLELinkAuthState owns them as whole transitions — retireLink, retireLinks(ownedBy:), permitRebind, permitRedundantRetirement — with the ownership question (bleQueue today, engine after the option-B flip) answered in one place. No behavior change; the one call-site reordering (redundant retirement computes the survivor before the cooldown check instead of after) is outcome-equivalent since the cooldown only ever recorded when a survivor existed. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Split identity-link bindings out of the physical link store BLELinkStateStore owned two different kinds of truth: what physical links exist (CB handles, connect lifecycles, characteristics, stream assemblers) and who each link belongs to (peer bindings in both roles plus the preferred-peripheral reverse map for directed sends and fanout collapse). The bindings now live on BLELinkBindings — same bleQueue ownership, whole-transition methods, direct tests for the rotation reverse-map cleanup and the preferred-link survivor repair that were previously only exercised end to end. Composed operations that need both truths (remove-with-repair, direct link state, the subscribed- central snapshot, bind-only-live-links) live on the transport as explicitly bleQueue-confined helpers. This is the structural half of the option-B boundary flip (docs/BLE-ARCHITECTURE-V3.md): ownership of the bindings can now move to the engine without touching what-links-exist. An audit of every physical clear/remove found three sites (emergency clear, both unauthorized branches) that needed explicit binding-clear pairing under the split — each now clears both. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> * Fix iOS-gated constructors and preserve containment cooldowns on reset CI caught what the macOS SwiftPM build cannot see: two #if os(iOS) sites still passed the peerID field that slice B1 removed from BLEPeripheralLinkState (willRestoreState in BLEService and armPendingBackgroundConnects in BLERadioController). Both fixed and verified with a local iOS simulator xcodebuild. Codex also caught a real regression: BLELinkAuthState.removeAll() cleared the rebind/retirement cooldown maps, which the original panic and emergency reset paths deliberately left alive. A stable CoreBluetooth UUID must not earn a fresh rebind allowance just because the session state around it was wiped. removeAll() now clears only the proofs and revalidation epochs, and BLELinkAuthStateTests pins the survival invariant along with the other auth-state transitions. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com> --------- Co-authored-by: jack <jackjackbits@users.noreply.github.com> Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
bitchat
A decentralized peer-to-peer messaging app with dual transport architecture: local Bluetooth mesh networks for offline communication and internet-based Nostr protocol for global reach. No accounts, no phone numbers, no central servers. It's the side-groupchat.
Getting a copy you can trust
Install from the App Store, or build from source you have verified. A compiled build from anywhere else cannot be verified — see Verifying bitchat for how to check source against the per-release hash manifest, and for what to do if that is the only build you can get.
This matters more than it usually would: this repository has been the target of takedown demands, and when a repository or releases page disappears, mirrors appear that nobody can check.
License
This project is released into the public domain. See the LICENSE file for details.
Features
- Dual Transport Architecture: Bluetooth mesh for offline + Nostr protocol for internet-based messaging
- Location-Based Channels: Geographic chat rooms using geohash coordinates over global Nostr relays
- Intelligent Message Routing: Automatically chooses best transport (Bluetooth → Nostr fallback)
- Decentralized Mesh Network: Automatic peer discovery and multi-hop message relay over Bluetooth LE
- Privacy First: No accounts, no phone numbers, no servers. Note that the mesh does use a persistent per-device identifier derived from your identity key — see the whitepaper on identity and metadata for what a nearby radio can observe
- Private Message End-to-End Encryption: Noise Protocol for mesh, BitChat private envelopes for Nostr fallback
- IRC-Style Commands: Familiar
/slap,/msg,/whostyle interface - Universal App: Native support for iOS and macOS
- Emergency Wipe: Triple-tap to instantly clear all data
- Performance Optimizations: LZ4 message compression, adaptive battery modes, and optimized networking
Technical Architecture
BitChat uses a hybrid messaging architecture with two complementary transport layers:
Bluetooth Mesh Network (Offline)
- Local Communication: Direct peer-to-peer within Bluetooth range
- Multi-hop Relay: Messages route through nearby devices (max 7 hops)
- No Internet Required: Works completely offline in disaster scenarios
- Noise Protocol Encryption: End-to-end encryption, with forward secrecy for live sessions (store-and-forward mail is sealed without it — see the whitepaper)
- Binary Protocol: Compact packet format optimized for Bluetooth LE constraints
- Automatic Discovery: Peer discovery and connection management
- Adaptive Power: Battery-optimized duty cycling
Nostr Protocol (Internet)
- Global Reach: Connect with users worldwide via internet relays
- Location Channels: Geographic chat rooms using geohash coordinates
- 290+ Relay Network: Distributed across the globe for reliability
- BitChat Private Envelopes: App-specific encrypted private messages over Nostr relays
- Ephemeral Keys: Fresh cryptographic identity per geohash area
BitChat's private-envelope format is proprietary and is not NIP-17,
NIP-44, or NIP-59 compatible. It uses Nostr as a relay transport but only
interoperates with BitChat clients: private payloads travel inside kind-1059
events whose v2:-prefixed content is a BitChat-specific XChaCha20-Poly1305
construction, not NIP-44 encryption.
Channel Types
mesh #bluetooth
- Transport: Bluetooth Low Energy mesh network
- Scope: Local devices within multi-hop range
- Internet: Not required
- Use Case: Offline communication, protests, disasters, remote areas
Location Channels (block #dr5rsj7, neighborhood #dr5rs, country #dr)
- Transport: Nostr protocol over internet
- Scope: Geographic areas defined by geohash precision
block(7 chars): City block levelneighborhood(6 chars): District/neighborhoodcity(5 chars): City levelprovince(4 chars): State/provinceregion(2 chars): Country/large region
- Internet: Required (connects to Nostr relays)
- Use Case: Location-based community chat, local events, regional discussions
Direct Message Routing
Private messages use intelligent transport selection:
-
Bluetooth First (preferred when available)
- Direct connection with established Noise session
- Fastest and most private option
-
Nostr Fallback (when Bluetooth unavailable)
- Uses recipient's Nostr public key
- BitChat's app-specific private-envelope encryption
- Routes through global relay network
-
Smart Queuing (when neither available)
- Messages queued until transport becomes available
- Automatic delivery when connection established
For detailed protocol documentation, see the Technical Whitepaper.
Setup
Option 1: Using Xcode
open bitchat.xcodeproj
For a signed device build, create your ignored local configuration and replace the example team ID with your Apple Developer Team ID:
cp Configs/Local.xcconfig.example Configs/Local.xcconfig
Local.xcconfig.example derives unique app and App Group identifiers from that
team ID. The entitlement files already reference $(APP_GROUP_ID), so tracked
project or entitlement files do not need to be edited.
Useful command-line checks from the repository root:
# macOS Debug build without signing
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)" \
-configuration Debug CODE_SIGNING_ALLOWED=NO build
# Full SwiftPM test suite
swift test
# iOS simulator tests
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (iOS)" \
-sdk iphonesimulator \
-destination 'platform=iOS Simulator,name=iPhone 17' test
If iPhone 17 is unavailable, choose an installed simulator from:
xcodebuild -showdestinations -project bitchat.xcodeproj -scheme "bitchat (iOS)"
Option 2: Using just
brew install just
just check
just run
just build and just run use the current bitchat (macOS) scheme and keep
Xcode output in the ignored .DerivedData/ directory. They never patch source,
project, configuration, or entitlement files.
just clean removes only .DerivedData/ and .build/. It does not invoke Git
or restore tracked files, so uncommitted work is preserved. just test runs the
SwiftPM suite and just test-ios runs the iPhone 17 simulator suite.
Localization
- App localizations live in
bitchat/Localizable.xcstrings. - Share extension strings are separate in
bitchatShareExtension/Localization/Localizable.xcstrings. - Prefer keys that describe intent (
app_info.features.offline.title) and reuse existing ones where possible. - Run
xcodebuild -project bitchat.xcodeproj -scheme "bitchat (macOS)" -configuration Debug CODE_SIGNING_ALLOWED=NO buildto compile-check any localization updates.