BurnPony for Android

Self-destructing encrypted notes where the recipient installs nothing. You write a note, set self-destruct rules, and share one link; it decrypts client-side in any browser. The server stores only ciphertext it cannot read — the decryption key travels in the URL fragment, which browsers never transmit. No accounts anywhere.

This repository is the Android sender app (Kotlin, Jetpack Compose). The recipient side is the web viewer.

The protocol, server, viewer, and test vectors live elsewhere

norsehorse-dev/BurnPonyiOS is canonical for the wire-format specification (PROTOCOL.md, also live at burnpony.app/protocol), the PHP server, the single-file viewer, and the shared cross-implementation test vectors. This repository references them and does not fork them. The shared/ directory carries a copy of the canonical vectors so :core:test is self-contained; the files in BurnPonyiOS are ground truth.

Modules and flavors

• core/ — the BurnPony v1 crypto core: pure Kotlin/JVM, zero third-party dependencies (JCA primitives, hand-rolled RFC 5869 HKDF, deterministic payload serializer, strict base64). Byte-compatible with the CryptoKit and WebCrypto implementations, proven by the vector suite.
• app/ — the Compose app. Two flavors on the dist dimension:
  • standard — Play distribution; adds firebase-messaging for read-receipt push. Firebase is initialized manually; the google-services Gradle plugin is not applied.
  • foss — F-Droid distribution; no Google artifacts anywhere in the dependency graph (./gradlew :app:dependencies --configuration fossReleaseRuntimeClasspath shows none). Read receipts arrive via status polling.

Building

JDK 17+, Android SDK 36. The Gradle wrapper pins everything else.

./gradlew :core:test                 # crypto gate: 100% vector parity
./gradlew :app:assembleFossDebug
./gradlew :app:assembleStandardDebug

Release builds read signing material from app/keystore.properties (untracked); without it the release output is unsigned, which is what F-Droid's verification build expects.

Trust model, briefly

Every note gets a per-note management token, issued at creation, capable of burn/status/expiry-change but never decryption, and stored server-side only as a SHA-256 hash. The optional note label never leaves the device. The full framing is on the protocol page.

License

Apache-2.0. BurnPony is part of the pony family of privacy tools: encryption you can inspect instead of taking a developer's word for it.