Amber/README.md

Amber: Nostr event signer for Android

Amber is a nostr event signer for Android. It allows users to keep their nsec segregated in a single, dedicated app. The goal of Amber is to have your smartphone act as a NIP-46 signing device without any need for servers or additional hardware. "Private keys should be exposed to as few systems as possible as each system adds to the attack surface," as the rationale of said NIP states. In addition to native apps, Amber aims to support all current nostr web applications without requiring any extensions or web servers.

Desktop

Amber also runs on Windows, macOS and Linux as a NIP-46 signer built with Compose for Desktop. It supports the same accounts, permissions and bunker connections as the Android app (minus NIP-55, which is Android-only IPC). See desktop/README.md for build and usage instructions.

Current Features

• Offline
• Use nip-46 or make an addendum in nip-46
• Improve the UI (currently it's showing a text with the raw JSON of the event)
• Check if we can use Amber to sign the events of web applications
• Change the sign button to just copy the signature of the event
• Use content provider to sign events in background when you checked the remember my choice option on android
• Support for multiple accounts

Download and Install

Contributing

Please read CONTRIBUTING.md before opening a pull request. If an AI coding assistant wrote a large part of your change, also read CONTRIBUTING-WITH-AI.md.

Issues can be logged on: https://gitworkshop.dev/greenart7c3@greenart7c3.com/Amber

GitHub issues and pull requests here are also welcome. Translations can be provided by editing the strings.xml files under app/src/main/res/values-<locale>/ and opening a pull request.

You can also send patches through Nostr using GitStr to this nostr address

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.

Development with Codex Web

This repository includes reusable Codex Web environment scripts so cloud tasks can bootstrap the Android build without manual setup. In the Codex Web environment settings, use:

bash .codex/setup.sh

as the setup script, and optionally use:

bash .codex/maintenance.sh

as the maintenance script for cached containers. The setup script installs or verifies Java 21, bootstraps the Android command-line SDK, installs Android API 36/build-tools 36.0.0, accepts SDK licenses, and warms Gradle dependencies for the default free debug unit-test sources.

Security and Verification

🔐 All releases are cryptographically signed with GPG for your security.

Before installing any APK from our releases, we strongly recommend verifying its authenticity to ensure it hasn't been tampered with.

📋 View Release Verification Guide

The verification process involves:

1. Importing our GPG public key
2. Verifying the release manifest signature
3. Checking file integrity with SHA256 hashes

GPG Key Details:

• Key ID: 44F0AAEB77F373747E3D5444885822EED3A26A6D
• Fingerprint: 44F0 AAEB 77F3 7374 7E3D 5444 8858 22EE D3A2 6A6D
• User ID: greenart7c3 <greenart7c3@proton.me>

Quick verification:

# Import the signing key
gpg --keyserver hkps://keys.openpgp.org --recv-keys 44F0AAEB77F373747E3D5444885822EED3A26A6D

# Verify a release (example for v1.0.0)
gpg --verify manifest-v1.0.0.txt.sig manifest-v1.0.0.txt

⚠️ Security Notice: Only download releases from this official GitHub repository. If GPG verification fails, do not install the APK and report it as a security issue.

Verifying Reproducibility of Amber

To confirm that the Amber build is reproducible, follow these steps:

1. Run the following command to build the image with no cache and specified version:

docker build -t amber-repro --progress=plain --no-cache --build-arg VERSION=v4.0.2 --build-arg APK_TYPE=free-arm64-v8a .

2. After the image is built, run the container:

docker run --rm amber-repro

3. You should see the following message indicating success:

APKs match!

Verifying Reproducibility of Amber Desktop

Every desktop download can be rebuilt from its tag and compared with the published file using desktopdiff.py. It compares what is inside: every path, file, symlink and executable bit must match, along with the installer's own scripts and tables (.deb maintainer scripts, .rpm scriptlets and dependencies, MSI custom actions, registry keys and shortcuts). Timestamps, owners and the installers' build dates are not compared, since they depend on when and where the files were packed. Packages are unpacked, never installed or run.

The app ships the Java runtime of the JDK it was built with, so a rebuild must use the same Temurin release. Print it from the download you are checking (--jdk takes any of the files below):

python3 desktopdiff.py --jdk Amber-X.Y.Z-linux-x86_64.tar.xz

21.0.12.1+1-LTS means Temurin jdk-21.0.12.1+1. Use the .tar.gz / .zip archive of that release, not its installer, which is packaged differently.

Linux (.tar.xz, AppImage, .deb, .rpm)

1. Build the image with no cache, the release tag and that JDK as a Docker tag (drop -LTS, + becomes _). If it is wrong, the build stops and names the right one:

docker build -f Dockerfile.desktop -t amber-desktop-repro --progress=plain --no-cache --build-arg VERSION=vX.Y.Z --build-arg JDK=21.0.12.1_1 .

2. Run the container:

docker run --rm amber-desktop-repro

3. You should see Builds match! four times: for the tarball, the AppImage, the .deb and the .rpm. A Note: about the .deb's Depends or the .rpm's Requires doesn't fail the check: jpackage lists the distro packages that provide the app's libraries on the build machine, which change with the distro's updates.

Windows (.msi, .exe)

jpackage only builds for the OS it runs on, so rebuild on Windows x64:

1. Unzip the Temurin .zip and point JAVA_HOME at it.
2. Build the release:

git clone https://github.com/greenart7c3/Amber.git
cd Amber
git checkout vX.Y.Z
New-Item keystore.properties
.\gradlew.bat :desktop:packageMsi :desktop:packageExe

3. Compare in WSL or on any Linux machine with msitools installed (apt install msitools). desktopdiff.py reads the MSI with msitools rather than msiexec, which would run the package's own actions:

python3 desktopdiff.py Amber-X.Y.Z-windows-x64.msi desktop/build/compose/binaries/main/msi/Amber-X.Y.Z.msi
python3 desktopdiff.py Amber-X.Y.Z-windows-x64.exe desktop/build/compose/binaries/main/exe/Amber-X.Y.Z.exe

macOS (.dmg)

Rebuild on a Mac of the same architecture as the download (arm64 for Apple silicon, x64 for Intel):

1. Unpack the Temurin .tar.gz and export JAVA_HOME=<unpacked folder>/Contents/Home.
2. Build and compare:

git clone https://github.com/greenart7c3/Amber.git
cd Amber
git checkout vX.Y.Z
touch keystore.properties
./gradlew :desktop:packageDmg
python3 desktopdiff.py ~/Downloads/Amber-X.Y.Z-macos-arm64.dmg desktop/build/compose/binaries/main/dmg/Amber-X.Y.Z.dmg

Certificate fingerprint for AppVerifier

com.greenart7c3.nostrsigner
E8:AB:8C:69:33:3B:68:63:6D:D4:6C:E2:42:40:8C:79:55:3A:7F:D9:05:5D:05:4D:61:DA:AB:AB:AD:A5:3B:BF

fdroid

com.greenart7c3.nostrsigner
56:DC:63:19:96:A5:5C:22:84:79:04:48:C7:DC:9F:1D:D0:5D:F5:96:B2:CE:48:82:31:36:33:F5:60:2E:5F:E4

Usage

Check NIP 55 and NIP 46 for more information.

Contributors