Secure Messaging Apps and Group Protocols, Part 2

So useful to talk about protocols like this and a pleasure to read. I look forward to going through these protocols later today.

However, to take it there, I'd conjecture that the limit on the best possible group security is being able to verify the integrity of group membership on a per-message basis, and use some kind of forward secrecy / ratchet whereby the given message key can only be derived from being a verified member of the group of the time of the message.

The only way I think we know how to do that is with consensus proofs about the composition of the group membership. For each message, you would need to encrypt it with a group message key that is derived with an authenticated proof of group membership that includes only all authorized members. It's like there is a direct trade off between the complexity class of the protocol/algorithm, and the security guarantees of the protocol.

The best secuirty outcome is that only a member during the period of that message can recieve and disclose the plaintext, and without some way of diverisfying the plaintext per user, you don't know which user leaked it. The other limit appears to be that if you get a message from the group, you can't know who else is in the reciever group - only that the complete group may have r ecieved it.

Just for discussion sake, I think there may be some high level lemmas about the necessary trade offs in these protocols.

If you can get code to run on a server which can trigger Hertzbleed, beit a virtual server where you have no control over what other people run on their virtual server instance, or you can employ a virtual cpu like the NSO iMessage gif exploit but program virtual gif cpu to do more than whats detailed in the NSO iMessage gif exploit, do private messaging platforms like WhatsApp have much privacy? I know people like evidence including the legal system, most of the time, but stealth weapons have to be captured in order to obtain the evidence.