Self-hosted, end-to-end-encrypted, two-way file sync, keyed and authenticated entirely by your SSH keys.
secsec is the open-source, fully encrypted, no-frills alternative to iCloud, OneDrive, and Google Drive. One small binary is both client and server, and the server is blind: it stores only ciphertext and can never read or forge your data. Your SSH keys are the only credential: they do both the encryption and the authentication, so there are no accounts, no certificate authority, and no second password to manage. Already have a box you can SSH into? That's your server.
- Zero-knowledge. File contents, file names, and the directory structure are encrypted; the server holds only opaque, content-addressed blobs and sees their sizes (file chunks padded to powers of two).
- Live two-way sync. Edit on any device; a three-way merge keeps both sides of a conflict (no silent data loss), and each file keeps its last 8 versions by default.
- Post-quantum key wraps. The repository key is wrapped to each device with X-Wing (ML-KEM-768 ⊕ X25519), so the harvest-now-decrypt-later target is quantum-safe today.
- Just SSH keys.
~/.ssh/authorized_keysgates access and~/.ssh/id_ed25519is your identity and backup. No CA, no database, no accounts, no recovery secret. - Self-hosted, one binary. Client and server in a single self-contained executable with an embedded store.
- One repo, one synced tree. Every enrolled device converges on the same content, whatever the local folder is named.
Status: feature-complete and tested end to end, but not yet independently audited. The protocol is a bespoke construction over standard primitives; don't trust it with irreplaceable data until it has had a professional cryptographic review.
curl -fsSL https://raw.githubusercontent.com/nesdeq/secsec/main/install.sh | sh # client
curl -fsSL https://raw.githubusercontent.com/nesdeq/secsec/main/install.sh | sh -s -- --server # serverLinux and macOS on x86_64 and aarch64. Windows: download the .zip from
releases. From source: cargo build --release --locked.
The installer verifies every download against the release's SHA256SUMS (and its build provenance
with gh attestation verify when the GitHub CLI is signed in), puts secsec in
SECSEC_INSTALL_DIR, else /usr/local/bin when writable, else ~/.local/bin, and asks what it needs
on the terminal (also under curl | sh). Re-running a mode updates it in place.
- Client (default): the binary, the desktop UI (the GNOME extension or the macOS menu-bar app), and an optional guided link of a folder to a server. Without a UI on Linux it offers a systemd user service for the folder instead.
--server: the binary andsecsec serveas a user service (systemd with lingering on Linux, a LaunchAgent on macOS), with its data directory, UDP port, and the device keys it admits.--binary: only the binary.
Flags answer the questions up front: --folder, --link HOST[:PORT], --pin, --invite,
--no-ui for the client; --dir, --port, --authorize "ssh-ed25519 ..." for the server;
--version TAG, and -y to take flags and defaults without prompting. --help lists them all.
Every device authenticates with its own SSH key (~/.ssh/id_ed25519; run ssh-keygen -t ed25519 if
you have none). The server admits only keys listed in its ~/.ssh/authorized_keys.
# Server: authorize your devices, then serve a directory (udp/8899)
cat device.pub >> ~/.ssh/authorized_keys
secsec hostpin --serve /srv/data # the host pin devices check
secsec serve /srv/data
# First device: creates the repository
secsec sync ~/cloud --server server.example --pin <host pin>
# Another device: pair with a one-time invite code
secsec invite ~/cloud # on an enrolled device
secsec sync ~/cloud --server server.example --pin <host pin> --invite # on the new device; prompts for the codeWithout --pin the first connection trusts the server's key on first use and prints its pin for you
to compare. A folder is remembered after its first sync: afterwards, just secsec sync ~/cloud.
| Command | |
|---|---|
secsec serve [dir] [--port P] |
Run the blind server; it admits only keys in ~/.ssh/authorized_keys. |
secsec sync [dir] [--server H[:P]] [--pin PIN] [--invite [CODE]] [--once] |
Link a folder (first time) and keep it in two-way sync. |
secsec stop [dir] |
Stop the sync running for a folder. |
secsec status [dir] |
Whether a folder's sync is running and how it last went, as key=value lines. |
secsec invite [dir] |
Print a one-time code and pair a new device. |
secsec devices [dir] |
List enrolled devices with their SSH key fingerprints. |
secsec revoke <device> [dir] [-y] |
Revoke a device (and the devices it granted since you last checked), rotating the key away from them. |
secsec hostpin [dir] / secsec hostpin --serve <dir> |
Print the host pin a folder trusts, or a server's own. |
secsec log [path] |
The repository's change log, or one file's or folder's versions. |
secsec restore <path> [version] |
Write an earlier version into the folder (default: the previous one). |
secsec reset [dir] [-y] |
Remove secsec's own state for a folder and/or serve directory; your files and ~/.ssh stay. |
dir defaults to the current directory; stop, status, invite, devices, revoke, and
hostpin also accept any path inside a synced folder, and log and restore take paths relative to
where you are inside one. sync, invite, devices, revoke, log, and
restore load your device key: --key <file> picks another than ~/.ssh/id_ed25519, and
--passphrase-stdin reads its passphrase from stdin instead of prompting (for launchers: the
passphrase travels over a pipe, never the command line). Every command takes --help.
Tunable settings (retention, poll interval, QUIC timeouts, server rates and limits) live in
~/.config/secsec/secsec.config ($XDG_CONFIG_HOME/secsec/ when set), written with defaults on first
use and clamped to safe ranges on load. Retention prunes old versions automatically inside sync.
install.sh --server sets the server up as a service. By hand on Linux, the installer's units are:
systemctl --user enable --now secsec-serve.service # the server
systemctl --user enable --now secsec-sync@$(systemd-escape -p ~/cloud).service # a client folder
loginctl enable-linger # run from boot, without a loginA service cannot type a passphrase, so a headless client needs a key without one:
put SECSEC_OPTS=--key <file> in ~/.config/secsec/sync@<escaped path>.conf. Link the folder once by
hand first. On macOS the installer uses LaunchAgents (com.secsec.serve, and com.secsec.ui for the
menu-bar app).
Optional panel apps: a GNOME Shell extension and a macOS menu-bar app. Each asks for your
key passphrase at login, runs secsec sync in the background (the passphrase travels over a pipe,
never the command line), lets you set the folder and SSH key, and shows the sync's status. Link the
folder once by hand, then let the UI drive it. Setup: ui/README.md.
Files are split by keyed content-defined chunking and sealed object by object with a fully committing AEAD (CTX/CMT-4 over ChaCha20-Poly1305), each addressed by a keyed BLAKE3 of its plaintext and re-verified on every fetch. Membership is an append-only, SSHSIG-signed roster anchored to a repository fingerprint that travels inside the authenticated invite; the repository key is wrapped to each device's post-quantum X-Wing keyslot and checked against a commitment in that roster, so the server can never hand a device a forged key or a fake repository. The repository head is signed and encrypted; the blind server only compare-and-swaps opaque blobs. Transport is QUIC + TLS 1.3 to a pinned, self-signed host key, with every request individually signed.
The primitives are standard (Ed25519/SSHSIG, X25519, ML-KEM-768, BLAKE3, ChaCha20-Poly1305, TLS 1.3);
the protocol that combines them is bespoke. The full threat model (malicious server, network
attacker, revoked device, stolen client), with the mechanism behind every claim, is in
secsec-Design.md.
cargo fmt --all -- --check
cargo clippy --locked --all-targets --all-features -- -D warnings
cargo test --locked --all --all-features
cargo xtask vectors --checkA strictly layered Rust workspace (primitives, then the object plane, roster, and sync plane, then
transport, then client and server), with committed known-answer vectors and a cargo-fuzz target per
decoder. Crate map, CI, and risk register: secsec-Implementation.md.
Designed, built, and reviewed by Claude Opus 4.8 (1M context), Claude Fable 5, and humans, fully in the open, every line on GitHub. Nothing hidden; read the code and the design spec.