> Bob's answers contain the "delivery receipt".
I've not seen any specific claims about the mechanism for the delivery receipt - can you link me to this?
It's not even clear to me that the delivery receipt is signed.
It's also not clear that the server must forward all the delivery receipts before it forwards the later replies.
Could it just eat them all?
EDIT: after a quick look at the spec¹, it seems that it supports out-of-order messages, meaning the server could selectively eat receipts.
[1] https://whispersystems.org/docs/specifications/doubleratchet...
So, given that, it would seem that a compromised server could pull a whole conversation (if people overlook the single tick mark), as claimed in the article?
seems like it, yes
Ah. If that is so (and it's not obvious - clearly you can get delivery or even read receipts without Bob sending an answer), then it would seem that a bad server could only intercept a long monologue, indeed, but not a conversation.
(Greetings from HS F13 :)
No, it can't do this, because Bob's answers contain the "delivery receipt".
Hence, the attack doesn't work on conversations.
EDIT to reply: messages are sequential and "delivery receipts" are messages, so it would be visible if the attacker dropped some but not all messages. AFAICT.