Delta Chat
Delta Chat is a private messenger that uses email protocols and servers for transport. It combines chat-oriented clients, automatic OpenPGP encryption, and SecureJoin contact verification.
Federation by reuse
Users can communicate through purpose-built chatmail relays or compatible ordinary email servers. Current chatmail profiles use random addresses and keep group and contact metadata inside encrypted messages. Transport relays still see sender and recipient addresses and message size, and Delta Chat does not yet implement sealed sender.
The security profile differs in classic email mode: some incoming or outgoing messages may lack E2EE and are marked accordingly.
Current cryptographic boundary
Delta Chat uses E2EE by default in current releases and SecureJoin to resist active key substitution. Its current production encryption does not provide PFS. Autocrypt v2 is scheduled to add forward secrecy and post-quantum protection, so those properties should not be claimed before deployment.
Secure and decentralized communication stacks compares this reuse strategy with dedicated networks and federated chat protocols.