Can you guys suggest some reliable and secure selfhosted IM service? I’m kinda in a very bad spot right now, so any centralized messaging wouldn’t really work. And yeah, state sponsored mass surveillance is a question of concern. Sorry for odd phrasing, just really at a loss.
I heard of matrix, XMPP (heard good things about snikket.org), SimpleX and even some IRC wizardry over TOR. And I actually tried matrix (synapse server), but found it not reliable enough - sometimes skips a notification, periodic troubles with logging in, weird lack of voice calls on mobile client, and some other irritating, tiny hiccups. I’m open to any suggestion, really, even open to trying matrix once again. Just, please, describe why you think one option is better than the other.
And just FYI, use case is simply texting with friends and family, while avoiding state monitoring. Nothing nefarious
Signal. There’s nothing better for security, ease of use, and features. It’s a drop in replacement for texts and imessage and facetime.
Thanks for reply. Unfortunately, we can’t use it, should be exclusively selfhosted service :( I do like Signal, tho, great app
That’s rough. Signal is the only app that can actually be trusted to resist state monitoring because it has a successful history of it.
I guess another option to throw into the pool is https://docs.cwtch.im/ then. It’s new though, and not as easy to use.
Be aware that the Signal Foundation still runs servers for the signal service. If a state actor compromises them, e2ee is no longer guaranteed.
It’s unlikely encryption would be compromised since the keys never leave the device. The user’s device would have to be compromised for that. Decrypting messages on Signal servers without the keys takes too many resources to be feasible en masse, even for a state actor. And the current app has no method to transfer those private/decryption keys.
But Signal is not private. It is only secure. Two totally different things. A bad actor could uniquely identify a user and what users they have communicated with and how often, just not the content of the messages. That metadata is stored on the Signal servers and the company has access. That is the tradeoff for ease of use and keeping malicious accounts to a minimum vs an anonymous IM app.
Op specifically asked about a self-hosted option. I think it was fair to comment that Signal wouldn’t satisfy this requirement.
Right, which is why I didn’t reply to op. I replied to a threaded comment that stated that Signal e2ee could be compromised by a compromised server, which is incorrect. Only privacy could be compromised, not e2ee. The specific threaded comment I replied to didn’t mention that it didn’t satisfy OP, which I also agree with.
A compromised server would allow the server to man-in-the-middle all new connections (as in, if Alice and Bob have never talked to each other before, the Server/Eva can MITM the x3dh key exchange and all subsequent communication). That’s why verifying your contact’s signatures out-of-band is so important.
(And if you did verify signatures in this case, then the issue would immediately be apparent, yes.)
Edit: I was wrong. See below.
This too would likely require compromising at least one of the devices or at the very least compromising both users’ ISPs or some other fairly detailed and highly targeted attack, but none of that would require compromising Signal’s servers and would make any system’s key exchanges vulnerable, even self hosted systems.
Simply compromising Signal’s servers might allow disrupting key exchanges from succeeding and thus making it impossible for those users to communicate at all, but not MITM really, at least if we assume there aren’t defects in the client apps.
The key exchange is much more complex than something like TLS and designed specifically so that the server can’t interfere. With true e2ee the key never passes through the server. This isn’t like many other apps that say e2ee, but really mean end to server gets one key and server to end gets another and decryption and re-encryption happens at the server to allow users to access older messages on new devices and stuff like that. Signal just connects the users to each other. The apps do the rest.
They could probably do something if they totally took over the entire Signal network infrastructure, but it’s definitely not something they could do undetected. But if a government took over the entire infrastructure, security conscious people would stop using it immediately thus not really worth the monetary and political cost. Otherwise China and others would have already done that to all secure communications. And again, not Signal specific.
Huh - you’re right. I went back to Signal’s X3DH spec because I was sure I was right, but it seems I misremembered how the “prekey bundles” work: Users publish these to the server, allowing (in my original assumption) for the server to just swap them out for a server/attacker-controlled key bundle for each Alice and Bob.
However, when Alice wants to send Bob an initial message and she gets a forged prekey bundle, Bob will simply not be able to derive the same key and communication will fail, because Bob knows what his SPK private key is, while the server only knows the public key.