Natrium

Natrium is a Kotlin Multiplatform library that wraps Wire's Kalium SDK to provide a simplified API for secure citizen-to-government communication.

Natrium is not a rewrite of Kalium. It is a thin facade that exposes only what partners need to build secure messaging clients.

Project Structure

natrium/
  natrium-core/     KMP library (the SDK) — see natrium-core/docs/ for SDK documentation
  natrium-cli/      JVM CLI app (Clikt), reference implementation

Targets

• JVM (desktop / server)
• Android (minSdk 26)
• iOS (arm64 + simulator)

All shared code lives in natrium-core/src/commonMain/ and must compile for all three targets.

Building

Prerequisites: JDK 21+, Android SDK (compileSdk 36).

# Build all targets
./gradlew build

Usage

Add natrium-core as a dependency from Maven Central:

// build.gradle.kts
dependencies {
    implementation("schwarz.opensource.natrium:natrium-core:<version>")
}

See natrium-core/README.md for API usage and code examples.

Documentation

• Getting Started — install, initialize, first login
• API Reference — full public-type and method listing

See natrium-core/README.md for the complete documentation index and design overview.

License

The Natrium SDK (the wrapper code in this repository) is licensed under the European Union Public Licence v. 1.2 only (EUPL-1.2). See LICENSE for the full licence text and NOTICE for attribution.

Kalium SDK — not licensed under the EUPL

Natrium depends on Wire’s Kalium SDK (currently the Maven artifact schwarz.opensource.natrium:logic). No portion of the Kalium SDK is licensed under the EUPL-1.2, either as a standalone component or as incorporated in Natrium.

The Kalium SDK may only be used under:

• the GNU General Public License v3.0, as published by Wire; or
• a commercial licence obtained from Wire Swiss GmbH.

Linking or combining Natrium with the Kalium SDK does not cause any copyleft effect of the EUPL-1.2 to extend to Kalium. Recipients who use Kalium without a commercial licence from Wire remain subject to the GPL-3.0 and to the licences of Kalium’s third-party dependencies.

Publication of Natrium under the EUPL-1.2 is authorised by a commercial licence agreement between Schwarz Digits and Wire Swiss GmbH. That agreement does not grant any Kalium rights to recipients of Natrium.