SimpleX chat

Federated, private, secure, decentralized

SimpleX chat prototype is a thin terminal UI on top of SimpleXMQ message broker that uses SMP protocol and SMP agent protocol.

See simplex.chat website for chat demo and the explanations of the system and how SMP protocol works.

Table of contents

• Features
• Installation
  • Download chat client
  • Build from source
    • Using Docker
    • Using Haskell stack
• Usage
  • Running the chat client
  • How to use SimpleX chat
  • Access chat history
• Roadmap
• Disclaimer
• License

Features

• 1-to-1 chat with multiple people in the same terminal window.
• Auto-populated recipient name - just type your messages to reply to the sender once the connection is established.
• Demo SMP server available at smp1.simplex.im:5223 - you can deploy your own server (smp-server executable in simplexmq repo).
• No global identity or any names visible to the server(s), ensuring full privacy of your contacts and conversations.
• E2E encryption, with RSA public key that has to be passed out-of-band (see How to use SimpleX chat).
• Message signing and verification with automatically generated RSA keys.
• Message integrity validation (via including the digests of the previous messages).
• Authentication of each command/message by SMP servers with automatically generated RSA key pairs.
• TCP transport encryption using SMP transport protocol.

RSA keys are not used as identity, they are randomly generated for each contact. 2048 bit keys are used, it can be changed to 4096-bit in code via rsaKeySize setting.

Installation

Download chat client

Download the chat binary for your system from the latest stable release and make it executable as shown below.

Linux and MacOS

chmod +x <binary>
mv <binary> ~/.local/bin/dog-food

(or any other preferred location on PATH).

On MacOS you also need to allow Gatekeeper to run it.

Windows

move <binary> %APPDATA%/local/bin/dog-food.exe

Build from source

Using Docker

On Linux, you can build the chat executable using docker build with custom output:

$ git clone git@github.com:simplex-chat/simplex-chat.git
$ cd simplex-chat
$ DOCKER_BUILDKIT=1 docker build --output ~/.local/bin .

Please note: If you encounter version `GLIBC_2.28' not found error, rebuild it with haskell:8.8.4-stretch base image (change it in your local Dockerfile).

Using Haskell stack

Install Haskell stack:

curl -sSL https://get.haskellstack.org/ | sh

and build the project:

$ git clone git@github.com:simplex-chat/simplex-chat.git
$ cd simplex-chat
$ stack install

Usage

Running the chat client

To start the chat client, run dog-food (as in eating your own dog food) from the terminal.

By default, app data directory is created in the home directory (~/.simplex, or %APPDATA%/simplex on Windows), and SQLite database file smp-chat.db is initialized in it.

The default SMP server is smp1.simplex.im#pLdiGvm0jD1CMblnov6Edd/391OrYsShw+RgdfR0ChA= (base-64 encoded string after server host is the transport key digest) - it is pre-configured in the app.

To specify a different file path for the chat database use -d command line option:

$ dog-food -d my-chat.db

If you deployed your own SMP server(s) you can configure client via -s option:

$ dog-food -s smp.example.com:5223#KXNE1m2E1m0lm92WGKet9CL6+lO742Vy5G6nsrkvgs8=

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).

Run dog-food --help to see all available options.

How to use SimpleX chat

This diagram shows how to connect and message a contact:

Once you have started the chat, use /add <name1> to create a new connection and generate an invitation (<name1> is any name you want to use for that contact). The add command will output an invitation. Send this invitation to your contact via any other channel.

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 use /connect <name2> <invitation> to accept the connection (<name2> is any name that the accepting contact wants to use for you).

Once the contact has used the /connect command, a connection is established and both parties are notified.

They would then use @<name> <message> commands to send messages. One may also press Space or just start typing a message to send a message to the contact that was the last.

If your contact is disconnected, restart the chat client - it may happen if you lose internet connection.

Use /help in chat to see the list of available commands.

Access chat history

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.

You can search your chat history via SQLite database file:

sqlite3 ~/.simplex/smp-chat.db

Now you can query messages table, for example:

select * from messages
where conn_alias = cast('alice' as blob)
  and body like '%cats%'
order by internal_id desc;

Please note: SQLite foreign key constraints are disabled by default, and must be enabled separately for each database connection. 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.

Roadmap

1. Switch to application level chat protocol. This will allow to separate physical server connection management from logical chat contacts, and to support all common chat functions.
2. SMP queue redundancy and rotation in SMP agent protocol.
3. Symmetric groups support in SMP agent protocol, as a foundation for chat groups.
4. Delivery confirmation in SMP agent protocol.
5. Multi-agent/device data synchronisation - to use chat on multiple devices.
6. Synchronous streams support in SMP and SMP agent protocols, to support file transfer.
7. Terminal chat UI and mobile apps.
8. Scripts for simple SMP server deployment to hosting providers: Linode, Digital Ocean and Heroku.
9. Public broadcast channels.
10. Optional public contact/group addresses using DNS to establish connections, but not using it to send and receive messages - in this way you will keep all your contacts and groups even if you lose the control of the domain.

Disclaimer

System and protocol security have not been audited yet. As such, it is not advised to use SimpleX chat for high security communications.

License

AGPL v3