Amber/desktop

Amber Desktop (Windows, macOS, Linux)

A Compose for Desktop port of Amber that turns your computer into a NIP-46 remote signer ("bunker"). It shares the same Nostr stack as the Android app (the Quartz library, published for the JVM) and mirrors the mobile UI and permission model.

Features

• Multiple accounts: create a new key (NIP-06 seed words) or import an nsec, ncryptsec (NIP-49), raw hex key, or mnemonic
• NIP-46 signing over relays: connect, sign_event, get_public_key, ping, nip04_encrypt/decrypt, nip44_encrypt/decrypt, nip44v3_encrypt/decrypt, decrypt_zap_event, sign_psbt, switch_relays, logout
• Connect applications with a nostrconnect:// URI or by generating a bunker:// URI (with QR code) — each connection gets its own local key. Clicking a nostrconnect:// link opens Amber (Linux: registered per user via xdg-mime; macOS: declared in the app bundle's Info.plist)
• The same permission model as mobile: auto-accept / auto-reject rules per request type and event kind, time-bound grants (5 minutes … always), and per-application sign policies (basic / manual / sign everything)
• Per-application activity history and relay logs
• Default bunker relays management
• Tor (Settings → Tor setup), like the Android app: a built-in Tor daemon (kmp-tor, bundled for every OS) or an external SOCKS proxy such as the system tor service (port 9050) or Tor Browser (9150). Relay connections fail closed while built-in Tor is still starting, and switching modes redials every relay through the new route
• Local relays: localhost, LAN/VPN addresses (RFC 1918, link-local, CGNAT / Tailscale, IPv6 ULA) and .local / .lan / .home.arpa names get plain ws:// by default, always bypass Tor, and stay connected when the internet drops. An explicit ws:// relay on the public internet shows a cleartext warning
• System tray: closing the window minimizes Amber to the tray so it keeps answering requests (with Open / Lock now / Quit menu), and new approval requests raise a system notification and bring the window back — both configurable under Settings → Desktop. The tray uses the freedesktop StatusNotifierItem / AppIndicator protocol on Linux (via the dorkbox SystemTray library), so the icon shows on Wayland compositors such as Hyprland/Sway (through waybar's tray module) and on GNOME/KDE, not just X11. It needs an SNI host (e.g. waybar's tray module — note it may sit inside a group/drawer that you expand to reveal the icon) and the libayatana-appindicator runtime library; Amber automatically bridges the Ayatana library to the legacy libappindicator3 names dorkbox looks for, so no compat symlink is required. When no SNI host is on the session bus (or tray init takes too long), Amber skips the tray and logs why instead of blocking startup. AMBER_TRAY_TYPE=Gtk|AppIndicator|AutoDetect forces the backend and AMBER_DISABLE_TRAY=1 skips the tray entirely.
• Notifications go through the OS-native channel: the freedesktop notification daemon (mako, dunst, swaync, GNOME Shell, …) via notify-send or gdbus on Linux — so they work on Hyprland/Wayland — and the AWT tray notification on Windows and macOS (on macOS it is posted as Amber itself; allow it when macOS asks on first launch, or later under System Settings → Notifications → Amber)
• Mandatory passphrase lock (see Key storage below)
• Optional start-on-boot (Settings → Desktop), always starting locked — passphrase required before anything signs. Only offered for installed builds (not :desktop:run):
  • Windows: a per-user HKCU\Software\Microsoft\Windows\CurrentVersion\Run entry (no admin rights; also listed under Task Manager → Startup apps)
  • macOS: a per-user LaunchAgent (~/Library/LaunchAgents/com.greenart7c3.nostrsigner.plist) that runs Amber at login (listed under System Settings → General → Login Items & Extensions)
  • Linux: installs and enables a hardened systemd user service that starts Amber with the desktop session. No MemoryDenyWriteExecute (the JVM's JIT cannot run under it); the unit still gets ProtectSystem=strict, seccomp, NoNewPrivileges and friends
• Windows installer (MSI/EXE) adds a Start Menu entry and a desktop shortcut
• The window opens fitted to the screen's usable area (never under the taskbar) and remembers its size and maximized state
• Pending requests expire after 10 minutes (or at the request's NIP-40 expiration, if sooner), since NIP-46 clients stop waiting long before
• Native desktop layout: sidebar navigation with an account switcher, dense list views, and keyboard shortcuts
• Light/dark theme using the Amber palette
• Fully localized UI in 14 languages, switchable live under Settings → Language. The Android strings.xml translations (and event-kind descriptions) are bundled verbatim under resources/i18n/strings_<lang>.xml and loaded by core/Strings.kt; desktop-only strings live in strings_en.xml (prefixed d_) and fall back to English in other locales

Keyboard shortcuts

Ctrl on Windows/Linux, ⌘ on macOS:

Shortcut	Action
Ctrl/⌘ + 1–4	Switch between Incoming requests / Applications / Relays / Settings
↑ / ↓	Select a pending request (Incoming requests)
← / →	Cycle the selected request's "Remember" duration
Ctrl/⌘ + Enter	Approve the selected request with the chosen duration
Ctrl/⌘ + Shift + Enter	Reject the selected request
Escape	Leave the application detail view
Ctrl/⌘ + L	Lock
Ctrl/⌘ + M	Minimize to tray (keep running in the background)
Ctrl/⌘ + W	Same as Ctrl/⌘ + M
Ctrl/⌘ + Q	Quit

Not included: NIP-55 (nostrsigner: intents and the content provider) — that is Android IPC and does not exist on desktop. Web apps and other clients connect through NIP-46 instead.

Key storage

Private keys are encrypted at rest with AES-256-GCM. The AES key is held in a Java KeyStore (PKCS12) file under the application data directory:

• Windows: %APPDATA%\Amber
• macOS: ~/Library/Application Support/Amber
• Linux: $XDG_DATA_HOME/amber (or ~/.local/share/amber)

The keystore password is kept in the operating system's credential store:

• macOS: Keychain
• Windows: Credential Manager
• Linux: the freedesktop Secret Service (GNOME Keyring / KWallet over D-Bus)

so copying the data directory (or a backup of it) is not enough to unlock the keys. On systems without a secret daemon (headless Linux, minimal window managers) the password falls back to an owner-only file next to the keystore, and is migrated into the credential store automatically the first time one becomes available. The Settings screen shows which backend is in use.

Note the trust model: any process running as your OS user can request the secret from the credential store, so this protects against offline attacks (disk theft, leaked backups, copied data directories) rather than against malware running in your session. Use full-disk encryption and OS login protection too. If you move the data directory to another machine, also transfer the com.greenart7c3.nostrsigner entry from the credential store (or keep the legacy keystore.pass file).

Passphrase lock (mandatory)

Amber requires a passphrase: on first run a setup screen asks for one before anything else can be used, and installs that already have only the OS credential store are migrated to it on the next launch. The AES master key is then stored only wrapped (AES-256-GCM) under a key derived from your passphrase with Argon2id, in master.key.enc; the plain keystore and its credential-store/file password are deleted. The passphrase is never written anywhere. You can change it under Settings → Security, but there is no way to remove it and go back to unprotected storage.

With the lock on:

• Copying the data directory (or the credential store) is useless — without the passphrase there is no way to decrypt the keys.
• The per-account database (connected applications, permission grants, request history, relay logs) is also encrypted at rest with the master key — AES-256-GCM, with an AMBERENC1: header — so the metadata about which apps you sign for stays private too. Enabling the passphrase re-encrypts existing data immediately. (settings.json and accounts.json stay plaintext, but the private keys inside accounts.json are always encrypted with the master key.)
• Amber asks for the passphrase at startup and auto-locks after an idle timeout — 1 hour by default, selectable (5 min / 15 min / 1 hour / never) under Settings → Security — or immediately via Lock now. Locking evicts all key material from memory and disconnects the relays, so no request can be signed until you unlock again.
• Logging out of an account (which deletes its key from this device) asks for the passphrase first.

Residual risk it cannot remove: while unlocked, the keys are in the process's memory, so malware that can scrape another process's memory or log your keystrokes in your session could still capture them — that is inherent to any software signer on a general-purpose OS. Hardware-backed, per-signature consent (Touch ID / Windows Hello / TPM) would be the next step and is tracked as future work.

If you forget the passphrase there is no recovery — restore your keys from their nsec or seed-word backup instead.

Run and build

./gradlew :desktop:run                                # run from source
./gradlew :desktop:createDistributable                # runnable app image
./gradlew :desktop:packageDeb                         # Linux .deb
./gradlew :desktop:packageRpm                         # Linux .rpm
./gradlew :desktop:packageMsi                         # Windows .msi (build on Windows)
./gradlew :desktop:packageExe                         # Windows .exe (build on Windows)
./gradlew :desktop:packageDmg                         # macOS .dmg (build on macOS)
./gradlew :desktop:packageDistributionForCurrentOs    # whatever fits the host

jpackage can only produce installers for the OS it runs on, so release builds are made per-platform. Linux packaging needs fakeroot (deb) or rpm-build (rpm) installed.

Tests

./gradlew :desktop:test              # unit tests
AMBER_E2E=1 ./gradlew :desktop:test  # + a NIP-46 round-trip over a public relay