Messaging layer security: Encrypting a group chat

How do you keep the messages in a group chat secure? Messaging layer security (MLS).
The Double Ratchet algorithm provides end-to-end encryption for text messages between two people. But securing a group chat is much harder. MLS is the first standardized multi-party “key exchange” - a protocol for communication among groups of people or devices.
Resources:
Video on the Double Ratchet algorithm: • Double ratchet algorit...
MLS Working Group: messaginglayersecurity.rocks/
Created by Kelsey Houston-Edwards
Graphics by Ray Lux
Sponsored by Wire wire.com
Thanks to Britta Hale for the helpful conversation about MLS

[@oncedidactic]

So easy to understand the concepts and see deeper into the space of problems and solutions. Awesome!! Thanks!

[@eapiii]

Great set of videos

[@fusionsid]

Thank you for this and the other video, Im currently making a chat app and couldnt find any good videos explaining group encryption

[@hashtag9990]

hey gentleman, would you like to share your wisdom? we want to implement encryption in our app too, and we are not knowledgeable enough, ofcourse you don't have to share your wisdom for nothing.

[@tonpa]

Perfection!

[@charleskhenry]

Amazing.

[@lollol1992lollol]

00:00 - Introduction and the Challenge
00:54 - some Ideas how to solve it
00:54 - Parallelized Conversation
01:40 - Key Systems
02:17 - Messaging Layer Security (MLS) (Tree System)
03:37 - Key System
05:00 - Key Schedule
06:50 - Root Key change
09:53 - Remove Group Member
11:13 - Conclusion

[@hashtag9990]

How to expand the tree when new users join in? I mean I can make a work around, but what is the standard way?
from the video, I'm pretty sure I misunderstood, when a new user is added to the existing empty nodes, the user recieves a welcome message with modified root key? So the new user will never know the original root key? How could the new user encrypt then? I don't think with a modified root key is possible to encrypt and decrypt with the original root key, because others have it

[@hashtag9990]

root key doesn't change but all the members need to maintain the state of the modified ratcheted key? when a user joins? because if they don't keep track of it, same modified key could be derived from the original root key? That just means changing the root key, with new derived key? I got that 100% wrong, but I don't understand

[@guzh]

It is unclear how F gets its private key at 6'16''. It is also unclear why the rachet can go up the tree as well as down the tree.

[@markcuello5]

HELP

[@leesweets4110]

Epic? Quit saying epic. Its clearly the other pronunciation. Because your way of doing it is ambiguous with another word.

[@PrecariousPosition]

I've never heard it aloud that way. How bizarre. I wouldn't have thought it was a controversial word

[@StevenAkinyemi]

Ikr. If pronouncing it as epic is ambigous, why not save us the confusion?