litert_crypto 0.3.1

Stop shipping your .tflite in plain sight. Encrypt LiteRT (TFLite) models at build time and decrypt them in memory only — with pluggable key providers.

Changelog

0.3.1

Documentation release — no code changes.

Prefer the CLI flow over the asset transformer for now: encrypt with dart run litert_crypto encrypt and register the .enc files as plain assets — the README and the example app follow this flow again.

Multi-asset builds using the asset transformer (added in 0.3.0) have been observed to crash on Windows — the parallel per-asset dart run processes race while staging native assets (reported as dart-lang/sdk#63933). The transformer remains available.

0.3.0

Build-time encryption via a Flutter asset transformer

• Transformer mode (--input/--output, invoked by the flutter tool) with optional --label, --key-id, --config args; the label defaults to the asset's file name.
• New keyparts command — (re)generates the key_parts_out Dart source without an encrypt run; rewrites when the key or key_parts_symbol changes.
• The config can live in pubspec.yaml as a top-level litert_crypto: section; a dedicated litert_crypto.yaml wins when both exist.
• With key_parts_out set, a build with stale or missing key parts fails with a keyparts hint — instead of failing at app runtime.
• Builds need the key file — on CI, provision .secrets/model_master.key from a secret; a missing key fails the build with that hint.
• Key rotation: bump --key-id in the transformer args (or flutter clean) — the build cache cannot see a key change. See docs/key-management.
• The loader names a plaintext TFLite model (TFL3) instead of raising a generic format error — it means the asset was bundled unencrypted.
• The first flutter build now compiles the BoringSSL host library (cmake + C compiler, NASM on Windows x64) — previously only flutter test and the CLI did. Cached after the first run.

0.2.1

Documentation release — no code changes.

• README reworked for readability: the Windows NASM requirement now has its own error → cause → fix walkthrough next to the CLI usage; key rotation and key_id are explained instead of name-dropped; several sections trimmed of internals that belong in the design docs.
• New in the repository (not part of the published package): tool/setup.ps1, a one-shot NASM check/install/PATH-repair script for Windows hosts.

0.2.0

The crypto engine is now native BoringSSL (package:webcrypto, dart:ffi) and the format is AES-256-GCM. Decryption is dramatically faster: about 1.2 ms/MB on an AES-NI desktop, so a 72 MB model decrypts in 87 ms. This is a clean break from 0.1.0 — re-encrypting your models is the whole migration (details under Breaking).

Breaking:

• LRTC format version 2 — AES-256-GCM (12-byte IV, 16-byte tag, header as additional authenticated data) replaces AES-CTR + HMAC-SHA256. Files written by 0.1.0 are refused with a re-encrypt hint; re-running dart run litert_crypto encrypt is the whole migration.
• LrtcCodec.decryptInPlace / decryptBufferInPlace / decryptWithProviderInPlace are gone — GCM verifies and decrypts in one native call, which has no in-place variant. LrtcEnvelope's cipherText/tag fields became sealed (ciphertext ‖ tag).
• SDK floors rose to Dart 3.10 / Flutter 3.38 (webcrypto builds BoringSSL via Dart hooks).
• Host builds (flutter test, CLI on a plain Dart VM) compile BoringSSL and need cmake + a C compiler, plus NASM on Windows x64. App builds compile it through Gradle/NDK/Xcode with nothing to configure.

Also:

• Decryption now runs on a worker isolate by default, so the calling isolate keeps rendering through it. Pass inIsolate: false (available on every loader entry point) to keep it inline.

0.1.0

Initial release.

• LRTC encrypted model format: AES-256-CTR with encrypt-then-MAC (HMAC-SHA256), HKDF-derived per-model subkeys, keyId for key rotation — plus a Flutter-free codec entrypoint (package:litert_crypto/codec.dart)
• EncryptedModel.fromAsset/fromFile/fromBuffer loader — decrypts in memory only, zeroes keys and plaintext after use, no inference-runtime dependency
• Key providers: EmbeddedKeyProvider (XOR parts), CallbackKeyProvider, RemoteKeyProvider (retries, single-flight, pluggable KeyCache), FallbackKeyProvider
• CLI: dart run litert_crypto init | keygen | encrypt, including generated EmbeddedKeyProvider source kept in sync with the key (key_parts_out)