> The mention of double ratchet is confusing and maybe worrying in the sense that it feels as though they don't understand what they're doing here. I'll start

> The mention of double ratchet is confusing and maybe worrying in the sense that it feels as though they don't understand what they're doing here. I'll start this by saying that I recognize your username from lots of good informative posts here over the years. But I think you're being unnecessarily harsh here, to the point of taking maybe the most uncharitable interpretation of the limited data that we have. We've spent the past 20 years telling people not to roll their own crypto. Is it really that bad when somebody takes that advice to heart? > I guess it can make sense to have the system automatically change the keys when participants leave, somehow, as this means a participant can't secretly eavesdrop calls they seem to have left. But I don't see how that's the double ratchet. They mentioned the Olm version of double ratchet. This usage scenario sounds a lot like ratcheting the sender keys in a Matrix group chat with Megolm. If you think that you might want to occasionally ratchet your keys (as speculated here [1]), then IMO it's better to grab something good (but possibly overpowered) off the shelf than to try to cobble together something yourself. Even if maybe you don't wind up using the hash-based ratchet very much. [1] https://news.ycombinator.com/item?id=22858476 https://news.ycombinator.com/item?id=22858476