Score:2

Glue between X3DH and Double-Ratchet

jp flag

While studying Signal and more particulartly X3DH and Double-Ratchet one particular apsect seems unspoken or not really documented. X3DH provides a shared secret however Double-Ratchet needs a shared secret and a public key.

In the Double-Ratchet documentation they say that either Alice can be the only Double-Ratchet initiator either Bob can be the iniatiator too if the shared secret (of X3DH) is used as the first chain key of the Double-Ratchet.

I place my study in a world where Alice and Bob can initiate the Double-Ratchet. As such they use the shared secret as their initial chain key. However against a passive adversary, if the X3DH shared secret has been compromised then the adversary will be able to read the first and second message of the Double-Ratchet (not more because of state healing). As such:

First and foremost, have I missed something ?

Are there studies on this particular aspect ?

ug flag
Only the first sending message(s) can be read. The first receiving message(s) will have ratchet initialised by sender's ratchet public key.
mangohost

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.