Amber

Your smartphone as a Nostr signing device. Keep your nsec secure in a dedicated app.

Overview

Amber is a Nostr event signer for Android that keeps your private key segregated from other apps. It turns your smartphone into a NIP-46 signing device without needing external servers or hardware.

Key Features

Key Isolation

┌─────────────────────────────────────────────────────────┐
│                   Without Amber                          │
├─────────────────────────────────────────────────────────┤
│                                                          │
│  App A ─── nsec ◄──► signs events                       │
│  App B ─── nsec ◄──► signs events                       │
│  App C ─── nsec ◄──► signs events                       │
│                                                          │
│  ⚠️  Every app has your key = More attack surface       │
│                                                          │
└─────────────────────────────────────────────────────────┘

┌─────────────────────────────────────────────────────────┐
│                    With Amber                            │
├─────────────────────────────────────────────────────────┤
│                                                          │
│  App A ──┐                                               │
│  App B ──┼──► Amber (nsec) ──► signs events             │
│  App C ──┘                                               │
│                                                          │
│  ✓ Only Amber has your key = Minimal attack surface     │
│                                                          │
└─────────────────────────────────────────────────────────┘

NIP-55 Integration

Android apps invoke Amber via NIP-55:

// From another Android app
val intent = Intent("com.greenart7c3.nostrsigner.SIGN_EVENT")
intent.putExtra("event", eventJson)
startActivityForResult(intent, REQUEST_CODE)

// Amber handles signing, returns result

NIP-46 Bunker

Use Amber as a remote signer for web apps:

1. Generate bunker connection string in Amber
2. Paste into web app login (e.g., Nostr Nests, Coracle)
3. Amber signs events over relay connection
4. Web app never sees your nsec

Connection string format:

bunker://npub...@relay.nsecbunker.com

Permission Management

Permission	Description
Sign events	Approve individual signatures
Remember choice	Auto-sign for trusted apps
Revoke	Remove app access anytime
Event types	Grant by kind (posts, DMs, etc.)

Multi-Account Support

• Multiple Nostr identities
• Quick account switching
• Per-account permissions
• Separate relay configurations

Security Model

┌─────────────────────────────────────────┐
│            Amber Security                │
├─────────────────────────────────────────┤
│                                          │
│  ┌────────────────────────────────────┐ │
│  │     Android KeyStore               │ │
│  │  ┌──────────────────────────────┐ │ │
│  │  │     nsec (encrypted)         │ │ │
│  │  └──────────────────────────────┘ │ │
│  └────────────────────────────────────┘ │
│                    │                     │
│                    ▼                     │
│  ┌────────────────────────────────────┐ │
│  │    Amber App                       │ │
│  │    - Decrypts only for signing     │ │
│  │    - Never exports raw key         │ │
│  └────────────────────────────────────┘ │
│                    │                     │
│                    ▼                     │
│  ┌────────────────────────────────────┐ │
│  │    Other Apps                      │ │
│  │    - Request signatures only       │ │
│  │    - Never see the nsec            │ │
│  └────────────────────────────────────┘ │
│                                          │
└─────────────────────────────────────────┘

Supported Apps

Android Apps (NIP-55)

App	Integration
Amethyst	Full support
0xChat	Full support
Voyage	Full support
Fountain	Full support
Pokey	Full support

Web Apps (NIP-46)

App	Integration
Nostr Nests	Bunker login
Coracle	Bunker login
Nostrudel	Bunker login
Habla	Bunker login
Snort	Bunker login

Installation

F-Droid

Available in the main F-Droid repository:

https://f-droid.org/packages/com.greenart7c3.nostrsigner/

GitHub Releases

Download APK directly:

https://github.com/greenart7c3/Amber/releases

Obtainium

Add repository URL for automatic updates.

Zap.store

Available in the Nostr-native app store.

Requirements

• Android 8.0 (API 26) or newer
• No Google Play Services required

Usage

Initial Setup

1. Install Amber from preferred source
2. Create new key or import existing nsec
3. Optionally set PIN/biometric lock

Connecting Apps

For Android apps:

1. Open the app (e.g., Amethyst)
2. Select "Login with Amber"
3. Amber opens for approval
4. Grant permissions

For web apps:

1. Open Amber
2. Go to Settings → Bunker
3. Copy connection string
4. Paste into web app login

Background Signing

Enable "Remember my choice" for trusted apps:

• Events sign automatically
• No interruption to workflow
• Revoke anytime in settings

Configuration

Relay Settings

Configure which relays Amber uses for NIP-46:

Settings → Relays → Add/Remove

Permissions Review

View and manage app permissions:

Settings → Connected Apps → [App Name]

Backup

Export encrypted backup:

Settings → Backup → Export (password protected)

Comparison

Feature	Amber	nos2x	nsec.app
Platform	Android	Browser	Web
NIP-55	Yes	No	No
NIP-46	Yes	No	Yes
Multi-account	Yes	Yes	Yes
Open source	Yes	Yes	Yes

Links

• GitHub: greenart7c3/Amber
• F-Droid: com.greenart7c3.nostrsigner
• NIP-55 Spec: nips.nostr.com/55

See Also

• Nostr Protocol — The protocol
• Amethyst — Android client with Amber support
• Alby — Browser extension alternative
• Decentralized Identity — The concept