Signal Desktop

Signal-Desktop is a cross-platform messaging application that provides end-to-end encrypted communication. It implements the Signal Protocol to secure messages and voice calls, ensuring that only intended recipients can access content. The application manages asynchronous key exchange and session initialization to maintain secure communication channels between parties who are not online simultaneously.

The project distinguishes itself through advanced cryptographic protections, including hybrid post-quantum security that combines classical elliptic curve cryptography with lattice-based algorithms to defend against future decryption threats. It further protects user privacy by obfuscating message headers with rotating keys, which prevents traffic analysis and the correlation of conversation participants. To ensure reliability over constrained networks, the application utilizes erasure-coded data transmission to reconstruct messages despite potential packet loss.

The software provides comprehensive data management and synchronization capabilities, allowing users to link desktop clients to mobile accounts for consistent conversation history. It secures local data through encrypted message archives and provides automated lifecycle management to handle message retention. The application also includes robust identity verification mechanisms, enabling users to authenticate correspondents via public key fingerprint comparison to prevent impersonation.

Features

Encrypted Messaging Platforms - Ships a cross-platform desktop client for private, end-to-end encrypted messaging and voice calls.
End-to-End Encrypted Messaging Frameworks - Provides end-to-end encrypted messaging to ensure that only intended recipients can access conversation content.
End-to-End Encryption - Provides end-to-end encrypted messaging to ensure only intended recipients can access conversation content.
Asynchronous Key Exchange Protocols - Implements asynchronous key exchange protocols to facilitate secure session establishment between parties who are not online simultaneously.
Cryptographic Protocols - Implements the Signal Protocol for asynchronous, forward-secret, and end-to-end encrypted messaging.
Post-Quantum Cryptography - Protects digital communications against future decryption threats using advanced post-quantum cryptographic security.
End-to-End Encryption - Implements end-to-end encryption to ensure that only intended recipients can access message content and metadata.
Ratchet Protocols - Implements symmetric-key and Diffie-Hellman ratchets to derive unique message keys for every transmission, ensuring forward secrecy.
Key Derivation Protocols - Derives new keys for every message to ensure forward secrecy and prevent decryption of past or future communications.
Multi-Device Synchronization - Links desktop and mobile accounts to maintain consistent conversation history and contact lists across devices.
Post-Quantum Key Exchange - Implements post-quantum key encapsulation to protect communication channels against future decryption threats.
Secure Multi-Device Synchronization - Coordinates encrypted state across multiple linked clients by securely distributing session keys and message history.
Message Synchronization - Synchronizes desktop clients with mobile accounts to maintain consistent conversation history across platforms.
Header Obfuscation - Protects message metadata by encrypting packet headers with rotating keys to prevent traffic analysis.
Encrypted Persistence - Secures message archives and user state on the local disk using strong encryption.
Digital Signature Schemes - Validates cryptographic signatures using elliptic curve mathematics to ensure message authenticity and integrity.
Encryption Key Management - Rotates identity and one-time keys to maintain forward secrecy and secure message initiation.
Hybrid Cryptographic Protocols - Integrates hybrid cryptographic ratchets combining classical and post-quantum algorithms for layered security.
Account Linking - Enables secure linking of desktop clients to mobile accounts via QR code scanning for synchronized history.
Identity & Key Management - Verifies correspondent identities via public key fingerprint comparison to prevent impersonation.
Key Agreement Protocols - Bootstraps messaging sessions by deriving initial root keys from established key agreement protocols.
Key Management Protocols - Publishes and retrieves prekey bundles to facilitate asynchronous session establishment.
Local Data Storage - Secures local message archives and conversation history to prevent unauthorized access on the device.
Session Lifecycle Management - Rotates and expires cryptographic sessions based on inactivity to maintain security and clean up stale device state.
Communication Clients - Desktop client for secure, encrypted messaging.
Communication Tools - Secure and private messaging application.
Media and Communication - Companion desktop app for Signal.
Collaboration Tools - Listed in the “Collaboration Tools” section of the Awesome Mac awesome list.
Erasure Coding Libraries - Utilizes erasure coding to ensure reliable message reconstruction over constrained or unreliable network connections.
Encrypted Backups - Encrypts local message archives to prevent unauthorized access if the physical device is compromised.
Message Authentication Systems - Applies ratcheted message authentication codes to verify the integrity and origin of key exchange payloads.
Message Encryption - Coordinates encrypted message state across multiple devices and asynchronous environments to ensure consistent communication.
Data Lifecycle Management - Manages message retention and storage efficiency through automated lifecycle policies for local records.
Data Transmission Reliability - Splits large cryptographic messages into robust chunks using erasure codes to ensure successful delivery.
Code Signing - Generates digital signatures using XEdDSA to ensure the authenticity and integrity of signed content.
Cryptographic Signature Verification - Validates XEdDSA digital signatures to confirm message origin and integrity.
Error Recovery Protocols - Handles decryption failures by requesting message re-transmission to ensure reliable delivery despite synchronization errors.
Account Migration Protocols - Transfers user message history and account information between devices to ensure continuity during setup.
Key Exchange Protocols - Exchanges large cryptographic keys in incremental chunks to ensure reliability over constrained networks.
Verifiable Random Function Signatures - Produces verifiable random function outputs alongside digital signatures to provide unique, deterministic message authenticity.
Signature Verification Tools - Confirms the validity of verifiable random function signatures to ensure message authenticity.

signalapp/Signal-Android

28,964View on GitHub

Signal-Android is an end-to-end encrypted messaging platform designed to ensure that only the sender and recipient can access communication content. The project provides a comprehensive framework for secure, asynchronous message initiation and key agreement, allowing users to establish private channels without requiring simultaneous online presence. It relies on a state machine architecture to manage communication epochs and authentication, ensuring consistent security transitions throughout the messaging lifecycle. The platform distinguishes itself through a hybrid cryptographic approach tha

signalapp/Signal-iOS

12,137View on GitHub

Signal-iOS is an encrypted messaging client that provides secure communication for voice calls, media, and text. It functions as a complete implementation of the Signal Protocol, utilizing end-to-end encryption to ensure that only intended recipients can access transmitted data. The application distinguishes itself through the integration of advanced cryptographic standards, including the use of elliptic curve cryptography for identity verification and digital signature validation. It employs a double ratchet key exchange mechanism to rotate encryption keys for every individual message, ensur

signalapp/libsignal

5,847View on GitHub

libsignal is a cryptographic library that implements the Signal Protocol, providing the core primitives for end-to-end encrypted messaging with forward secrecy and deniable authentication. It includes the Double Ratchet algorithm for iteratively deriving fresh encryption keys per message, and the X3DH key agreement protocol for establishing shared secrets between parties asynchronously. A session state machine maintains cryptographic state across message exchanges, supporting recovery and out-of-order delivery. The library extends beyond basic messaging encryption with capabilities such as ze

open-keychain/open-keychain

2,510View on GitHub

OpenKeychain is a mobile OpenPGP key manager and identity provider used for storing, importing, and organizing encryption keys and digital certificates. It serves as an end-to-end encryption client and digital signature tool for encrypting and decrypting text and files. The application functions as a central vault that provides encryption and decryption services to third-party apps, such as email clients and password managers. It enables secure public key exchange through online directory retrieval and QR code scanning. The project covers cryptographic identity verification, including the ab

signalappSignal-Desktop

Features

Open-source alternatives to Signal Desktop

signalapp/Signal-Android

signalapp/Signal-iOS

signalapp/libsignal

open-keychain/open-keychain

Star history

Open-source alternatives to Signal Desktop

signalapp/Signal-Android

signalapp/Signal-iOS

signalapp/libsignal

open-keychain/open-keychain