SimpleX chat prototype is a thin terminal UI on top of [SimpleXMQ](https://github.com/simplex-chat/simplexmq) message broker that uses [SMP protocols](https://github.com/simplex-chat/simplexmq/blob/master/protocol).
**We are building the most private and secure chat in the world** - open-source, decentralized, and without global identities of any kind. If you would like to support it, you can do so in the following ways:
- 🌟 **Star it on GitHub** - it's a great feedback you like it and helps us raise the visibility of the project.
- **Install the chat and try using it** - if you spot a bug it would help a lot if you could [raise an issue](https://github.com/simplex-chat/simplex-chat/issues).
- **Spread the word** - terminal chat is an [early-stage product](#disclaimer) while we stabilize the protocol - you can invite your friends for some fun chatting inside your terminal. We're using it right inside our IDEs as we are coding it 👨💻
- **Make a donation** via [opencollective](https://opencollective.com/simplex-chat) - the amount doesn't matter, we appreciate any donation!
- **Make a contribution to the project** - we're constantly moving the project forward and there are always lots of things to do.
We appreciate all the help from our contributors, thank you!
This is WIP implementation of SimpleX chat that implements a new network topology for asynchronous communication combining the advantages and avoiding the disadvantages of federated and P2P networks.
If you expect a software being reliable most of the time and doing something useful, then this is probably not ready for you yet. We do use it for terminal chat though, and it seems to work most of the time - we would really appreciate if you try it and give us your feedback.
**Please note:** The main differentiation of SimpleX network is the approach to internet message routing rather than encryption; for that reason no sufficient attention was paid to either TCP transport level encryption or to E2E encryption protocols - they are implemented in an ad hoc way based on RSA and AES algorithms. See [SMP protocol](https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#appendix-a) on TCP transport encryption protocol (AEAD-GCM scheme, with an AES key negotiation based on RSA key hash known to the client in advance) and [this section](https://github.com/simplex-chat/simplexmq/blob/master/rfcs/2021-01-26-crypto.md#e2e-encryption) on E2E encryption protocol (an ad hoc hybrid scheme a la PGP). These protocols will change in a consumer ready version to something more robust.
## Network topology
SimpleX is a decentralized client-server network that uses redundant, disposable nodes to asynchronously pass the messages via message queues, providing receiver and sender anonymity.
Unlike P2P networks, all messages are passed through one or several (for redundancy) servers, that do not even need to have persistence (in fact, the current [SMP server implementation](https://github.com/simplex-chat/simplexmq#smp-server) uses in-memory message storage, persisting only the queue records) - it provides better metadata protection than P2P designs, as no global participant ID is required, and avoids many [problems of P2P networks](https://github.com/simplex-chat/simplex-chat/blob/master/simplex.md#comparison-with-p2p-messaging-protocols).
Unlike federated networks, the participating server nodes do NOT have records of the users, do NOT communicate with each other, do NOT store messages after they are delivered to the recipients, and there is no way to discover the full list of participating servers - it avoids the problem of metadata visibility that federated networks suffer from and better protects the network, as servers do not communicate with each other. Each server node provides unidirectional "dumb pipes" to the users, that do authorization without authentication, having no knowledge of the the users or their contacts. Each queue is assigned two RSA keys - one for receiver and one for sender - and each queue access is authorized with a signature created using a respective key's private counterpart.
The routing of messages relies on the knowledge of client devices how user contacts and groups map at any given moment of time to these disposable queues on server nodes.
- Demo SMP servers available and pre-configured in the app - or you can [deploy your own server](https://github.com/simplex-chat/simplexmq#using-smp-server-and-smp-agent).
Once the chat client downloads, you can run it with `simplex-chat` command in your terminal.
Alternatively, you can manually download the chat binary for your system from the [latest stable release](https://github.com/simplex-chat/simplex-chat/releases) and make it executable as shown below.
If you get `simplex-chat: command not found` when executing the downloaded binary, you need to add the directory containing it to the [`PATH` variable](https://man7.org/linux/man-pages/man7/environ.7.html) (find "PATH" in page). To modify `PATH` for future sessions, put `PATH="$PATH:/path/to/dir"` in `~/.profile`, or in `~/.bash_profile` if that's what you have. See [this answer](https://unix.stackexchange.com/a/26059) for the detailed explanation on the appropriate place to define environment variables for `bash` and other shells.
For example, if you followed the previous instructions, open `~/.profile` for editing:
```sh
vi ~/.profile
```
And add the following line to the end:
```sh
PATH="$PATH:$HOME/.local/bin"
```
Note that this will not automatically update your `PATH` for the remainder of the session. To do this, you should run:
On Linux, you can build the chat executable using [docker build with custom output](https://docs.docker.com/engine/reference/commandline/build/#custom-build-outputs):
> **Please note:** If you encounter `` version `GLIBC_2.28' not found `` error, rebuild it with `haskell:8.10.4-stretch` base image (change it in your local [Dockerfile](Dockerfile)).
To start the chat client, run `simplex-chat` from the terminal. If you get `simplex-chat: command not found`, see [Troubleshooting on Unix](#troubleshooting-on-unix).
By default, app data directory is created in the home directory (`~/.simplex`, or `%APPDATA%/simplex` on Windows), and two SQLite database files `simplex.chat.db` and `simplex.agent.db` are initialized in it.
Running above, for example, would create `alice.chat.db` and `alice.agent.db` database files in current directory.
Default SMP servers are hosted on Linode (London, UK and Fremont, CA) - they are [pre-configured in the app](https://github.com/simplex-chat/simplex-chat/blob/master/src/Simplex/Chat/Options.hs#L40). Base-64 encoded string after server host is the transport key digest.
The base-64 encoded string in server address is the digest of RSA transport handshake key that the server will generate on the first run and output its digest.
You can still talk to people using default or any other server - it only affects the location of the message queue when you initiate the connection (and the reply queue can be on another server, as set by the other party's client).
Once you have started the chat, you will be prompted to specify your "display name" and an optional "full name" to create a local chat profile. Your display name is an alias for your contacts to refer to you by - it is not unique and does not serve as a global identity. In case different contacts chose the same display name, the chat client adds a numeric suffix to their local display names.
Once you've set up your local profile, enter `/c` (for `/connect`) to create a new connection and generate an invitation. Send this invitation to your contact via any other channel.
You are able to create multiple invitations by entering `/connect` multiple times and sending these invitations to the corresponding contacts you'd like to connect with.
The invitation has the format `smp::<server>::<queue_id>::<rsa_public_key_for_this_queue_only>`. The invitation can only be used once and even if this is intercepted, the attacker would not be able to use it to send you the messages via this queue once your contact confirms that the connection is established.
The contact who received the invitation should enter `/c <invitation>` to accept the connection. This establishes the connection, and both parties are notified.
They would then use `@<name> <message>` commands to send messages. You may also just start typing a message to send it to the contact that was the last.
To create a group use `/g <group>`, then add contacts to it with `/a <group> <name>`and send messages with `#<group> <message>`. Use `/help groups` for other commands.
> **Please note**: the groups are not stored on any server, they are maintained as a list of members in the app database to whom the messages will be sent.
### Sending files
You can send a file to your contact with `/f @<contact> <file_path>` - the recipient will have to accept it before it is sent. Use `/help files` for other commands.
SimpleX chat stores all your contacts and conversations in a local database file, making it private and portable by design, fully owned and controlled by you.
> **Please note:** SQLite foreign key constraints are disabled by default, and must be **[enabled separately for each database connection](https://sqlite.org/foreignkeys.html#fk_enable)**. The latter can be achieved by running `PRAGMA foreign_keys = ON;` command on an open database connection. By running data altering queries without enabling foreign keys prior to that, you may risk putting your database in an inconsistent state.
3. Privacy-preserving identity server for optional DNS-based contact/group addresses to simplify connection and discovery, but not used to deliver messages:
