XSF Discussion - 2022-04-08

Is there a way to auto subscribe to private pep nodes without putting them all in caps?

I was considering the use case where I have a private pep node per roster contact. Or is that the wrong technology to use in that case?

It is, you'd have one item per contact, rather than one node. ✏

ahh...i see

A "purely hypothetical" question: In an established omemo session, one side has "rewound" its omemo state to some point far in the past (= backup restored). The server archive doesn't hold _all_ the messages exchanged since then, oldest ones being purged. Is it possible to "fast-forward" the omemo state so as to be able to decrypt the more recent history, or was the purged part of history somehow essential to being able to do that?

in omemo messages can be skipped

but only until some amount as i recall it

but not sure anyone has tested this

i guess if this wasnt the case it would be very fragile

like one message missed and your session is dead

the fact that i have sessions that are years old would hint that its not that fragile

I think that's implementation dependent

IIRC Conversations can heal a gap of something like 1000 messages

its not really, we all use libsignal code, or ports of the code

nobody invents or modifies the crypto

Hmm. So, I take it as "if implementation is willing to forward the ratchet a gazillion of steps until it generates a key that can decrypt the oldest archived message, there's nothing in the crypto preventing that"

And that Conv. apparently stops trying after 1000 iterations ✏

mjk: No, because during message exchange its likely that the receiving chain is forwarded, which triggers a new key derivation including some randomness. Therefore an old backup would result in the omemo session breaking, resulting in a new session.

This property is the "breaking recovery" part of the signal protocol.

vanitasvitae: thanks for the expert insight. I assumed the randomness is pseudo-, and the PRNG's state is part of that backed up omemo state; apparently, not?

No, the PRNGs state is not saved

That would defeat the purpose :D

Okay

XEP-XXXX: Save OMEMO state and all messages un-encrypted on Apple's server to compete with iMessage

XEP-YYYY: Upload your private key to Google

Stahp