Tchap is a secure instant messaging platform designed for French public sector staff. It is fully developed, operated, and maintained by the Direction interministérielle du numérique (DINUM), under the authority of the Prime Minister, and hosted on sovereign cloud infrastructure managed by the French Ministry of the Interior.

Protocol and security architecture: Tchap is based on the open-source Matrix protocol, which is also adopted by several other European countries and administrations. It provides full end-to-end encryption (E2EE) between participants' devices: servers through which messages transit cannot decrypt them, and even technical administrators cannot access conversation content. The platform has received a formal security certification (homologation) following in-depth consultation with all French ministries and ANSSI (the French National Cybersecurity Agency).

It is released under the dual licences Apache Licence 2.0 (Matrix) and GNU AGPLv3 (Element).

Key features

• End-to-end encrypted direct messages and group rooms (salons)
• Integrated public sector directory searchable by name or email
• Clear visual distinction between internal agents and external guests
• Multi-device support (smartphones, computers) with real-time session synchronisation
• Remote device disconnection in case of loss or theft
• Message recovery protected by a user-only secret code, not stored on servers
• Personalised support from the DINUM team and regular onboarding webinars