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
• 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
• Light/dark theme following the mobile look

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 (stronger, opt-in)

Enable a passphrase under Settings → Security for defence that does not depend on the OS credential store. 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.

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.
• Amber asks for the passphrase at startup and can auto-lock after an idle timeout (5 min / 15 min / 1 hour / never) 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.

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