[elvisloops]

Strange that they are posting about the "signal ratchet" when they just removed it by launching cloud backups that use a static key? Since those cloud backups include disappearing messages, that feature completely undoes all of the forward secrecy in this protocol.

[dist-epoch]

Signal can't protect you against the other party you are communicating with. They can backup the conversation, or screenshot it, or take a photo of the screen with another camera. They could also retell in their words what you sent.

[immibis]

You know (with pretty high certainty) that your conversational partner is using Signal. The security level of Signal affects your estimation of the security level of your partner.

[uv-depression]

That backup system presumably uses symmetric encryption, which is not nearly as vulnerable to quantum-accelerated attacks.

[elvisloops]

Yes, but you don't need a complicated ratcheting protocol if you've eliminated forward secrecy in other ways. This post is about "post compromise security," but there is already no post-compromise security after the cloud backups feature