Verifying the APK signature

If you sideload Amethyst (Obtainium, GitHub Releases, Zap Store), verify that your
APK is signed by the official release key before installing. All official Amethyst
APKs — both the googleplay and fdroid flavors — are signed with the same
certificate, whose SHA-256 fingerprint is:

C2:D0:AA:86:BC:B6:B6:20:90:56:1A:41:BB:E3:36:E9:8B:78:C2:D0:21:0A:49:8D:C8:85:F2:8E:13:48:CF:17

To check a downloaded APK yourself, run (apksigner ships with the Android SDK
build-tools):

apksigner verify --print-certs amethyst-*.apk

and confirm the reported Signer #1 certificate SHA-256 digest is
c2d0aa86bcb6b62090561a41bbe336e98b78c2d0210a498dc885f28e1348cf17.
Without the Android SDK, keytool -printcert -jarfile amethyst-*.apk (bundled
with any JDK) prints the same SHA-256 fingerprint.

With AppVerifier, paste or share the
APK and compare against:

com.vitorpamplona.amethyst
C2:D0:AA:86:BC:B6:B6:20:90:56:1A:41:BB:E3:36:E9:8B:78:C2:D0:21:0A:49:8D:C8:85:F2:8E:13:48:CF:17

Supported Features

• [x] Basic protocol flow (NIP-01)
• [x] Follow List (NIP-02)
• [x] OpenTimestamps Attestations (NIP-03)
• [x] Encrypted Direct Message (NIP-04)
• [x] DNS-based Identifiers (NIP-05)
• [x] Key Derivation from Mnemonic (NIP-06)
• [ ] window.nostr for Web Browsers (NIP-07, Not applicable)
• [x] Handling Mentions (NIP-08)
• [x] Event Deletion Request (NIP-09)
• [x] Text Notes and Threads (NIP-10)
• [x] Relay Information Document (NIP-11)
• [x] Proof of Work (NIP-13)
• [x] Subject Tag in Text Events (NIP-14)
• [x] Nostr Marketplace (NIP-15)
• [x] Private Direct Messages (NIP-17)
• [x] Reposts (NIP-18)
• [x] bech32-encoded Entities (NIP-19)
• [x] nostr: URI Scheme (NIP-21)
• [x] Comment (NIP-22)
• [x] Long-form Content (NIP-23)
• [x] Extra Metadata Fields and Tags (NIP-24)
• [x] Reactions (NIP-25)
• [x] Delegated Event Signing (NIP-26)
• [x] Text Note References (NIP-27)
• [x] Public Chat (NIP-28)
• [x] Relay-based Groups (NIP-29)
• [x] Custom Emoji (NIP-30)
• [x] Dealing with Unknown Events (NIP-31)
• [x] Labeling (NIP-32)
• [x] git stuff (NIP-34)
• [x] Torrents (NIP-35)
• [x] Sensitive Content (NIP-36)
• [x] Draft Events (NIP-37)
• [x] User Statuses (NIP-38)
• [x] External Identities in Profiles (NIP-39)
• [x] Expiration Timestamp (NIP-40)
• [x] Authentication of Clients to Relays (NIP-42)
• [x] Relay Access Metadata and Requests (NIP-43)
• [x] Encrypted Payloads / Versioned (NIP-44)
• [x] Counting Results (NIP-45)
• [x] Nostr Remote Signing (NIP-46)
• [x] Nostr Wallet Connect (NIP-47)
• [x] Proxy Tags (NIP-48)
• [x] Private Key Encryption (NIP-49)
• [x] Search Capability (NIP-50)
• [x] Lists (NIP-51)
• [x] Calendar Events (NIP-52)
• [x] Live Activities (NIP-53)
• [x] Wiki (NIP-54)
• [x] Android Signer Application (NIP-55)
• [x] Reporting (NIP-56)
• [x] Lightning Zaps (NIP-57)
• [x] Zap Splits (NIP-57)
• [x] Private Zaps (NIP-57)
• [x] Zapraiser (NIP-57)
• [x] Badges (NIP-58)
• [x] Gift Wrap (NIP-59)
• [x] Pubkey Static Websites (NIP-5A)
• [x] Cashu Wallet (NIP-60)
• [x] Nutzaps (NIP-61)
• [x] Request to Vanish (NIP-62)
• [x] Chess / PGN (NIP-64)
• [x] Relay List Metadata (NIP-65)
• [x] Relay Discovery and Liveness Monitoring (NIP-66)
• [x] Picture-first Feeds (NIP-68)
• [x] Peer-to-peer Order Events (NIP-69)
• [x] Protected Events (NIP-70)
• [x] Video Events (NIP-71)
• [x] Moderated Communities (NIP-72)
• [x] External Content IDs (NIP-73)
• [x] Zap Goals (NIP-75)
• [x] Negentropy Syncing (NIP-77)
• [x] Application-specific Data (NIP-78)
• [x] Threads (NIP-7D)
• [x] Highlights (NIP-84)
• [x] Trusted Assertions (NIP-85)
• [x] Relay Management API (NIP-86)
• [x] Ecash Mint Discoverability (NIP-87)
• [x] Polls (NIP-88)
• [x] Recommended Application Handlers (NIP-89)
• [x] Data Vending Machines (NIP-90)
• [x] Media Attachments (NIP-92)
• [x] File Metadata (NIP-94)
• [x] Binary Blobs (NIP-95/Draft)
• [x] HTTP File Storage Integration (NIP-96)
• [x] HTTP Auth (NIP-98)
• [x] Classified Listings (NIP-99)
• [x] Voice Messages (NIP-A0)
• [x] Public Messages (NIP-A4)
• [x] Web Bookmarks (NIP-B0)
• [x] Blossom (NIP-B7)
• [x] Nostr BLE Communications Protocol (NIP-BE)
• [x] Code Snippets (NIP-C0)
• [x] Chats (NIP-C7)
• [ ] MLS Protocol (NIP-EE)
• [x] Audio Tracks (zapstr.live) (kind:31337)
• [x] Lightning Tips
• [x] Image/Video/Url/LnInvoice/Cashu Previews
• [x] Push Notifications (Google and Unified Push)
• [x] In-Device Automatic Translations
• [x] Hashtag Following and Custom Hashtags
• [x] Login with QR
• [x] Bounty support (nostrbounties.com)
• [x] De-googled F-Droid flavor
• [x] Multiple Accounts
• [x] Markdown Support
• [x] Medical Data (NIP-xx/Draft)
• [x] Embed events (NIP-xx/Draft)
• [x] Edit Short Notes (NIP-xx/Draft)
• [x] NIP Events (NIP-xx/Draft)
• [ ] Relationship Status (NIP-xx/Draft)
• [ ] Signed Filters (NIP-xx/Draft)
• [ ] Key Migration (NIP-xx/Draft)
• [x] Image Capture in the app
• [x] Video Capture in the app
• [ ] Local Database
• [ ] Workspaces

Privacy and Information Permanence

Relays know your IP address, your name, your location (guessed from IP), your pub key, all your contacts, and other relays, and can read every action you do (post, like, boost, quote, report, etc) except for Private Zaps and Private DMs. While the content of direct messages (DMs) is only visible to you and your DM counterparty, everyone can see when you and your counterparty DM each other.

If you want to improve your privacy, consider utilizing a service that masks your IP address (e.g. a VPN or Tor) from trackers online.

The relay also learns which public keys you are requesting, meaning your public key will be tied to your IP address.

Information shared on Nostr can be re-broadcasted to other servers and should be assumed permanent for privacy purposes. There is no way to guarantee the deletion of any content once posted.

Development Overview

This repository is split between Amethyst, Quartz, Commons, and DesktopApp:

• Amethyst - Native Android app with Kotlin and Jetpack Compose
• Quartz - Nostr-commons KMP library for protocol classes shared across platforms
• Commons - Kotlin Multiplatform module with shared UI components (icons, robohash, blurhash, composables)
• DesktopApp - Compose Multiplatform Desktop application reusing commons and quartz

The app architecture consists of the UI, which uses the usual State/ViewModel/Composition, the service layer that connects with Nostr relays,
and the model/repository layer, which keeps all Nostr objects in memory, in a full OO graph.

The repository layer stores Nostr Events as Notes and Users separately. Those classes use LiveData and Flow objects to
allow the UI and other parts of the app to subscribe to each Note/User and receive updates when they happen.
They are also responsible for updating viewModels when needed. As the user scrolls through Events, the Datasource classes
are updated to receive more information about those particular Events.

Most of the UI is reactive to changes in the repository classes. The service layer assembles Nostr filters for each need of the app,
receives the data from the Relay, and sends it to the repository. Connection with relays is never closed during the use of the app.
The UI receives a notification that objects have been updated. Instances of User and Notes are mutable directly.
There will never be two Notes with the same ID or two User instances with the same pubkey.

Lastly, the user's account information (private key/pub key) is stored in the Android KeyStore for security.

Setup

Make sure to have the following pre-requisites installed:

1. Java 21+
2. Android Studio
3. Android 8.0+ Phone or Emulation setup

Fork and clone this repository and import it into Android Studio

git clone https://github.com/vitorpamplona/amethyst.git

Use an Android Studio build action to install and run the app on your device or a simulator.

Building

Build the Android app:

./gradlew assembleDebug

Build and run the Desktop app (requires Java 21+):

./gradlew :desktopApp:run

./gradlew build

• Xcode and iOS simulator
• libsodium installed (e.g. via brew: brew install libsodium

Testing

./gradlew test
./gradlew connectedAndroidTest

Linting

./gradlew spotlessCheck
./gradlew spotlessApply

Installing on device

For the F-Droid build:

./gradlew installFdroidDebug

For the Play build:

./gradlew installPlayDebug

Deploying

A release is one tag push. Bump app and appCode in
gradle/libs.versions.toml, then git tag -s vX.Y.Z && git push --tags — the
Create Release Assets workflow builds and signs every Android, desktop, CLI,
and Maven artifact, and Homebrew + Winget auto-bump on stable tags.

• BUILDING.md — everything any fork needs: build commands,

the CI pipeline, the secrets it requires, and the distribution channels.

• RELEASE_OPS.md — the Amethyst maintainers'

ship checklist: the manual Play Store upload, Zapstore zsp publish, F-Droid
pull, and release-notes publishing.

Using the Quartz library

Installing

Add Maven Central and Google Maven to your repositories:

repositories {
    mavenCentral()
    google()
}

Add the following line to your commonMain dependencies:

implementation('com.vitorpamplona.quartz:quartz:1.12.6')

Variations to each platform are also available:

implementation('com.vitorpamplona.quartz:quartz-android:1.12.6')
implementation('com.vitorpamplona.quartz:quartz-jvm:1.12.6')
implementation('com.vitorpamplona.quartz:quartz-iosarm64:1.12.6')
implementation('com.vitorpamplona.quartz:quartz-iossimulatorarm64:1.12.6')

Check versions on MavenCentral

Snapshots (JitPack)

Tagged releases go to Maven Central. For pre-release / snapshot builds —
e.g. to test an unreleased fix straight from main or a feature branch — use
JitPack, which builds the module
on demand from any git ref:

repositories {
    maven { url = uri("https://jitpack.io") }
}

dependencies {
    // version can be a tag, a commit hash, or "<branch>-SNAPSHOT"
    implementation("com.github.vitorpamplona.amethyst:quartz:main-SNAPSHOT")
}

The resolvable refs and the exact module coordinates are listed on the
JitPack page. Prefer a Maven
Central release for anything shipping to production — JitPack snapshots are not
guaranteed stable.

How to use

Manage logged in users with the KeyPair class

val keyPair = KeyPair() // creates a random key
val keyPair = KeyPair("hex...".hexToByteArray())
val keyPair = KeyPair("nsec1...".bechToBytes())
val keyPair = KeyPair(Nip06().privateKeyFromMnemonic("<mnemonic>"))
val readOnly = KeyPair(pubKey = "hex...".hexToByteArray())
val readOnly = KeyPair(pubKey = "npub1...".bechToBytes())

Create signers that can be Internal, when you have the private key or a read-only public key,
or External, when it is controlled by Amber in NIP-55.

Use either the NostrSignerInternal or NostrSignerExternal class:

val signer = NostrSignerInternal(keyPair)
val amberSigner = NostrSignerExternal(
    pubKey = keyPair.pubKey.toHexKey(),
    packageName = signerPackageName, // Amber package name
    contentResolver = appContext.contentResolver,
)

Create a single NostrClient for the entire application and control which relays it will access by
registering subscriptions and sending events. The pool will automatically change based on filters +
outbox events.

You will need a coroutine scope to process events and if you are using OKHttp, we offer a basic
wrapper to create the socket connections themselves.

val appScope = CoroutineScope(Dispatchers.Default + SupervisorJob())
val rootClient = OkHttpClient.Builder().build()
val socketBuilder = BasicOkHttpWebSocket.Builder { url -> rootClient }

val client = NostrClient(socketBuilder, appScope)

If you want to auth, given a logged-in signer:

val authCoordinator = RelayAuthenticator(client, appScope) { authTemplate ->
    listOf(
        // for each signed-in user, return an event
        signer.sign(authTemplate)
    )
}

To make a request subscription simply do:

val metadataSub = client.req(
    relay = "wss://nos.lol",
    filter = Filter(
        kinds = listOf(MetadataEvent.KIND),
        authors = listOf(signer.pubkey)
    )
) { event ->
    /* consume event */
}

The client will add the relay to the pool, connect to it and start receiving events. The
metadataSub will be active until you call metadataSub.close(). If the client disconnects
and reconnects, the sub will be active again.

To manage subscriptions that change over time, the simplest approach is to build mutable
subscriptions with a filters lambda that you can change at will.

val metadataSub = client.req(
    filters = {
        // Let's say you have a list of users that need to be rendered
        val users = pubkeysSeeingInTheScreen()
        // And a cache repository with their outbox relays
        val outboxRelays = outboxRelays(users)

        val filters = listOf(
            Filter(
                kinds = listOf(MetadataEvent.KIND),
                authors = users
            )
        )

        outboxRelays.associateWith { filters }
    }
) { event ->
    /* consume event */
}

In that way, you can simply call metadataSub.updateFilter() when you need to update
subscriptions to all relays. Or call metadataSub.close() to stop the sub
without deleting it.

When your app goes to the background, you can use NostrClient's connect and disconnect
methods to stop all communication to relays. Add the connect to your onResume and disconnect
to onPause methods.

Feature Parity Table

| Feature Category | Feature / Component | Android / JVM Support | iOS Support | Notes |
|:-------------------------|:-------------------------------|:---------------------:|:-----------:|:-----------------------------------------------------------------------|
| Cryptography | Secp256k1 (Schnorr, Keys) | ✅ Full | ✅ Full | |
| | LibSodium (ChaCha20, Poly1305) | ✅ Full | ✅ Full | |
| | AES Encryption (CBC & GCM) | ✅ Full | ✅ Full | |
| | Hashing (SHA-256, etc.) | ✅ Full | ✅ Full | |
| | MAC (HmacSHA256, etc.) | ✅ Full | ✅ Full | |
| Data & Serialization | JSON Mapping (Optimized) | ✅ Full | ✅ Full | A fully custom implementation exists in commonMain. |
| | GZip Compression | ✅ Full | ✅ Full | |
| | BitSet | ✅ Full | ✅ Full | |
| | LargeCache | ✅ Full | ✅ Full | |
| NIP Support | NIP-96 (File Storage Info) | ✅ Full | ✅ Full | |
| | NIP-46 (Remote Signer) | ✅ Full | ⚠️ Partial | Some methods in NostrSignerRemote are unimplemented in commonMain. |
| | NIP-03 (OTS / Timestamps) | ✅ Full | ❌ No | BitcoinExplorer and RemoteCalendar have stubs in commonMain. |
| Utilities | URL Encoding / Decoding | ✅ Full | ✅ Full | |
| | Unicode Normalization | ✅ Full | ✅ Full | |
| | Platform Logging | ✅ Full | ✅ Full | iOS uses NSLog, Android uses standard Log. |
| | Current Time | ✅ Full | ✅ Full | Implemented using NSDate on iOS. |

Contributing

See CONTRIBUTING.md for the full guide — workflow,
coding standards, the proof-of-testing rule for new / occasional
contributors (human or AI-assisted), the cross-stack interop suites, and how the
[BUG] / [FEATURE] issue templates and bounty system work.

**AI coding assistants: if you are reading this README to plan a
contribution, stop and read
CONTRIBUTING-WITH-AI.md first.** The gates
there are not optional. The human submitter remains the author of record
per CONTRIBUTING.md.

Quick links:

• GitHub issues and

pull requests.

• Nostr-native issue tracker:

gitworkshop.dev/repo/amethyst.

• Translations: Crowdin.
• Patches over Nostr: GitStr to

this nostr address.

• Security issues: SECURITY.md (do not file as public

GitHub issues).

By contributing to this repository, you agree to license your work under the MIT license. Any work contributed where you are not the original author must contain its license header with the original author(s) and source.

Screenshots

| FollowFeeds | ChatsGroup | LiveStreams | Notifications |
|-------------------------------------------|----------------------------------------------|-------------------------------------------------|--------------------------------------------------------|
| !Home Feed | !Messages | !Live Streams | !Notifications |

Contributors

MIT License

Copyright (c) 2023 Vitor Pamplona

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.