signal-without-smartphone is an open-source desktop application created by Alexis Métaireau (almet) that allows users to register a primary Signal account and link it to Signal Desktop without needing a smartphone.

The main features and technical capabilities of this tool include:

• Smartphone-Free Account Registration: Performs the initial Signal account registration and acts as the primary device to link Signal Desktop as a secondary device. (Note: While it eliminates the need for a smartphone, a phone number capable of receiving SMS verification codes is still required during setup).

• Cross-Platform Desktop Packages: Provides pre-compiled, GUI-based installers for macOS (.dmg), Linux (.AppImage and standalone binary), and Windows.

• Native Rust Workspace (No JVM Required): Written entirely in Rust (95.4%) and Shell (4.6%), structured into signal-setup-core and the signal-setup GUI crates. This removes the requirement for a Java Virtual Machine (JVM) needed by alternative tools like signal-cli.

• Built-In Signal Protocol Cryptography: Handles key generation directly, including ACI/PNI identity keys, signed pre-keys, Kyber post-quantum (PQ) keys, ProvisionMessage envelopes (using ECDH, HKDF, AES-256-CBC, and HMAC), and X3DH + Double Ratchet sessions for device synchronization.

• Staging & Offline Demo Modes: Features a --staging flag to run tests against Signal's staging environment, as well as a --demo flag for fully offline GUI testing without contacting any servers.

• AGPL-3.0 License: Released as free, open-source software under the GNU Affero General Public License v3.0.