cargo build --release
./target/release/signal-setup

# Ubuntu / Debian
sudo apt install libxcb-render0-dev libxcb-shape0-dev libxcb-xfixes0-dev \
libxkbcommon-dev libssl-dev protobuf-compiler

# Fedora
sudo dnf install libxcb-devel libxkbcommon-devel openssl-devel protobuf-compiler

# Arch
sudo pacman -S libxcb libxkbcommon openssl protobuf

./target/release/signal-setup --staging

git clone https://github.com/signalapp/Signal-Desktop.git
cd Signal-Desktop
pnpm install
pnpm start

%%{init: {'theme':'default', 'themeVariables': {'background':'#ffffff'}}}%%
sequenceDiagram
    actor User
    participant App as App
    participant Server as Signal Server
    participant Desktop as Signal Desktop
    participant Store as Disk + Keyring

    Note over App: Step 0: Welcome (if saved accounts)

    rect rgb(235,245,255)
    Note over User,Server: Phase 1: Request verification code
    User->>App: Step 1: enter phone (+1234567890)
    App->>Server: POST /v1/verification/session
    Server-->>App: session.id (+ captcha_required?)
    alt Captcha required
        Note over App: Step 2 shown
        User->>App: solve captcha, paste it
        App->>Server: POST .../session/{id}/code (sms)
    else No captcha
        App->>Server: POST .../session/{id}/code (sms)
    end
    Server-->>User: SMS verification code
    end

    rect rgb(235,255,235)
    Note over User,Server: Phase 2: Verify & register account
    User->>App: Step 3: enter 6-digit code
    App->>Server: PUT .../session/{id}/code {code}
    Note over App: Generate keys: ACI/PNI identity,<br/>signed pre-keys, Kyber PQ keys,<br/>master/profile keys, password
    App->>Server: POST /v1/registration (account attrs + keys)
    alt 409 Device transfer available
        Server-->>App: 409 / DeviceTransferAvailable
        Note over App: warn, retry skipping device transfer
    else Success
        Server-->>App: registered
        App->>Store: save metadata (disk) + secrets (keyring)
    end
    end

    rect rgb(255,245,235)
    Note over User,Desktop: Phase 3: Link Signal Desktop
    User->>App: Step 4: launch Desktop, "Link to existing device"
    Desktop-->>User: shows QR code
    User->>App: paste QR image / link
    App->>Server: GET /v1/devices/provisioning/code
    Server-->>App: verification_code
    Note over App: Build ProvisionMessage (identity keys,<br/>profile/master key, code) →<br/>ECDH + HKDF + AES-256-CBC + HMAC
    App->>Server: PUT /v1/provisioning/{ephemeral_id} (envelope)
    Server-->>Desktop: deliver envelope / register as device 2
    loop Poll up to 60s
        App->>Server: GET /v2/keys/{aci}/2
        Server-->>App: device 2 pre-keys (when ready)
    end
    Note over App: send_linked_device_sync():<br/>X3DH + Double Ratchet session,<br/>encrypt empty contacts SyncMessage
    App->>Server: PUT /v1/messages/{aci} (encrypted sync)
    Server-->>Desktop: SyncMessage / leaves "Syncing…"
    end

    App-->>User: Step 5 : 🎉 Setup complete

Signal Without Smartphone
Copyright (C) 2026 Alexis Métaireau

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published
by the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.