Backpeer

Encrypted backups on other people's computers.

Backpeer backs up your files in encrypted form to the machines of other users, and gives back the disk space you lend in return. Files are split into fragments with Reed–Solomon erasure coding, so the network keeps them available even when individual machines go offline, and repairs the missing pieces automatically.

Status: early development. The project is at the MVP stage: formats and APIs still change, there has been no external security audit yet, and there are no releases to install. Treat the code as work in progress, not as a product.

Русская версия.

How it works

• Zero-knowledge encryption. Everything is encrypted on your machine before it leaves it: XChaCha20-Poly1305 for data, Argon2id for passwords, Ed25519 for signatures, BLAKE2b for hashing (libsodium through FFI). Keepers store opaque fragments and never see file names or contents.
• Erasure coding instead of copies. Each backup segment is split into n = 20 fragments and stays readable from any k = 10 of them. When fragments are lost, the coordinator schedules repair and the network rebuilds them.
• Hybrid architecture. The coordinator stores metadata, placement, audits and reputation. The encrypted fragments travel directly between the client and the keepers over TCP, UDP hole punching or a relay, in a Noise XX channel.
• Two background processes on the client. node is the keeper daemon, agent runs scheduled backups; the desktop app is a UI on top of their local APIs.

The keeper daemon is a plain Dart binary and runs headless, including on NAS devices and single-board computers.

Repository layout

Path	Package	What it is
packages/core	core	Cryptography, erasure coding, chunking, data formats, networking
packages/protocol	protocol	Protobuf schemas and generated code
packages/cli	cli	Command-line client
packages/daemon_kit	daemon_kit	Shared daemon code: local API, log, directory lock
packages/node	node	Keeper daemon
packages/agent	agent	Backup agent (scheduled backups, verification, restore)
packages/coordinator	coordinator	Coordinator server
packages/relay	relay	Relay for peers without incoming connections
apps/app	app	Desktop application (Flutter)
test-vectors	—	Test vectors for the formats and the protocol

Every package except apps/app is plain Dart without Flutter.

Building

You need FVM, melos and lefthook; the Flutter version is pinned in .fvmrc.

fvm install          # Flutter and Dart from .fvmrc
lefthook install     # git hooks: formatting, analyzer, dependency rule
melos bootstrap      # dependencies of all packages
melos run check      # formatting, analyzer and tests
melos run build-exe  # cli, node and agent into build/bin/<os>-<arch>/

Run flutter and dart through fvm flutter ... and fvm dart ..., or use .fvm/flutter_sdk/bin directly. Linux packages (AppImage, .deb, .rpm) are built by tool/linux_package/build.sh; the macOS app and .dmg by melos run macos:build on a Mac with Xcode.

The coordinator needs PostgreSQL; its configuration is a YAML file plus FS_COORDINATOR_* environment variables.

Documentation

The specifications of the crypto, the data formats and the protocol are being prepared for publication separately, together with the operator and user documentation. Until then, the code and the test vectors are the reference.

Running a keeper node in Docker — installation, pairing with an account and day-to-day management — is covered in docs/install/docker.en.md.

Security

The zero-knowledge property is a design goal, and the code that implements it is here for review — but no independent audit has been performed yet. Do not use Backpeer as the only copy of anything you cannot afford to lose.

License

GNU Affero General Public License v3.0 or later — see LICENSE. Third-party components keep their own licenses.

Contributing

See CONTRIBUTING.md. Issues and pull requests are welcome; please keep in mind that the project is small and the maintainer's time is limited.