XMPP - Extensible Messaging and Presence Protocol
- Extensible - because you can extend functionality with XEPs (XMPP Extension Protocol)
- Messaging - because you can send messages with it
- Presence - because you can broadcast your online status and last read message indicator
- Protocol - Because it's a protocol, not software. Like ARM is an architecture, but they don't do CPUs
XMPP is a decentralised messaging protocol.
Different servers can communicate with each other.
Wide range of (mostly useless) XMPP clients exists.
(defragmentation like in the Linux world)
JID - Jabber Identifier
JID is your address (takes the form of an email address)
What is Jabber: Jabber.org is the original IM service based on XMPP and one of the key nodes on the XMPP network.
Because of the "history", everyone calls XMPP address a JID.
Because XMPP (kind of) works like email (but not exactly), different servers can communicate with each other.
- therealtrump - This is your "username"
- @ - Like with email, it separates username and server address
- mylittlebrony.fbi - This is the server you have account on
If firstname.lastname@example.org wants to send a message to email@example.com, it goes like this:
(I think that's how it works - not sure though!!)
- Alice sends a message (internally to her server)
- her server (fbi.gov) tries to reach cia.gov
- When reached successfully, fbi.gov sends a message (XML file) to cia.gov
- cia.gov accepts the file and assigns it to bob
- cia.gov sends an update to bob's client - showing the message
MUC - Multi-User Chat
Link to a XEP-0045: https://xmpp.org/extensions/xep-0045.html
Basically allows to have a group chat.
Group chats are called MUCs
There are 2 types of MUCs
- Public - where if you join, you can assign a nickname to yourself. Others don't know your JID
OMEMO is not available in Public MUCs
- Private - You must be added. Everyone knows your JID. You know everybody's JIDs
OMEMO is available in Private MUCs
OMEMO - OMEMO Multi-End Message and Object Encryption
It is an open encryption standard based on the Double Ratchet Algorithm and the Personal Eventing Protocol (PEP, XEP-0163).
OMEMO offers future and forward secrecy and deniability with message synchronization and offline delivery.
The OMEMO protocol offers many-to-many encrypted chat, offline messages queuing, forward secrecy, file transfer, verifiability and deniability at the cost of slightly larger message size overhead.
In short: It's an encryption thing that encrypts your message for each chat participant
(be it 1-on-1 or in a MUC)
Each device/client has a key that is shared to other chat members.
When you send a message, the message is encrypted FOR EACH MEMBER
THIS IS NOT EXACTLY HOW IT WORKS BUT IT WORKS SOMETHING LIKE THAT!!!!
In order to send a photo, your server has to have "Sending photos enabled".
When you send a photo, the photo is saved on your server and then the server sends the link to fetch it.
If servers have no storage assigned, or have sending photos disabled, you won't be able to send a photo.
Even if Sending photos is disabled, if you get a photo from an user, whose server allows to send photos,
you can, of course, download and view that photo, because it's handled by your client.
You are just fetching the photo from sender's server.
Voice & Video calling
1-on-1: Available depending on client capabilities.
MUC: I think it's not available (yet).