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Given MiTM, etc attacks, why does this particular statement not sit well with me? "Any discussion on end-to-end encryption in XMPP should begin with a reminder

Given MiTM, etc attacks, why does this particular statement not sit well with me? "Any discussion on end-to-end encryption in XMPP should begin with a reminder that in a federated system end-to-end encryption is not always necessary. When you trust your provider encrypting the transport layer is sufficient."

e12e 10y ago
If you trust the CA system (eg https, imaps) and your provider follows the spec and forces ssl, there isn't any particular mitm danger. Like if you use mail internally in a domain, eg Gmail, outlook.com etc - there's no obvious mitm attack surface. Users logs into Gmail over https or imaps, emails user2@gmail either via https or smtps - and user2 logs in the same way (similar for self-hatred [lol, there were a few autocorrect errors, leaving this one in - appropriate for "self-hosted"] email). As far as I know xmpp federation is "point2point", and the current standard demands ssl. So user1@jabber1.tld talking to user2@jabber2.tld will have the communication protected by the CA system and TLS from client1 via server1 to server2 down to client2. It is a system of many devices, each of which might be compromised, but traditional mitm isn't the biggest danger in this case.
Freak_NL 10y ago
Key here is "not always". If two users trust the intermediate chain of servers that have access to their messages, then transport layer security is indeed sufficient; that already safeguards against unauthorised links in the chain (the man in the middle). On the other hand, if absolute confidentiality is a concern, end-to-end encryption is required. XMPP does not rule out either approach. End-to-end encryption matters of course, but it is a lot more relevant when one single mega-corporation is in control of every server messages pass through (e.g., WhatsApp). But if, say, you and I decide to run our own XMPP-servers and communicate thus, it may be sufficient to ascertain that a secure channel exists between our servers and between our clients and their servers.

e12e 10y ago

If you trust the CA system (eg https, imaps) and your provider follows the spec and forces ssl, there isn't any particular mitm danger. Like if you use mail internally in a domain, eg Gmail, outlook.com etc - there's no obvious mitm attack surface. Users logs into Gmail over https or imaps, emails user2@gmail either via https or smtps - and user2 logs in the same way (similar for self-hatred [lol, there were a few autocorrect errors, leaving this one in - appropriate for "self-hosted"] email). As far as I know xmpp federation is "point2point", and the current standard demands ssl. So user1@jabber1.tld talking to user2@jabber2.tld will have the communication protected by the CA system and TLS from client1 via server1 to server2 down to client2. It is a system of many devices, each of which might be compromised, but traditional mitm isn't the biggest danger in this case.

Freak_NL 10y ago

Key here is "not always". If two users trust the intermediate chain of servers that have access to their messages, then transport layer security is indeed sufficient; that already safeguards against unauthorised links in the chain (the man in the middle). On the other hand, if absolute confidentiality is a concern, end-to-end encryption is required. XMPP does not rule out either approach. End-to-end encryption matters of course, but it is a lot more relevant when one single mega-corporation is in control of every server messages pass through (e.g., WhatsApp). But if, say, you and I decide to run our own XMPP-servers and communicate thus, it may be sufficient to ascertain that a secure channel exists between our servers and between our clients and their servers.