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"simply facilitates delivery of the public keys" is the pitfall here - how do you verify that you're actually swapping pubkeys with the intended recipient? Sure
by Piskvorrr 9y ago
"simply facilitates delivery of the public keys" is the pitfall here - how do you verify that you're actually swapping pubkeys with the intended recipient? Sure, you could hardcode server's pubkey (uh-oh), but then you still only know that you're swapping pubkey with someone who says "I am Bob" through a known server, without any guarantee that the other user is not Mallory who will then MITM the conversation (i.e. pose as Bob for you and as you for Bob).
- nstart 9y agoCurious though. Wasn't that the exact same issue people raised a stink about with Whatsapp? Signal has a prompt to verify when a key changes on the other person's device? I think the only solution they have is to use a QR code to verify that the exchanged keys are the same? I'm very new to all of this so curious if any of that is actually connected
- Piskvorrr 9y agoYes. Key management is not so simple.
- nstart 9y agoFair enough. Thank you so much for replying by the way. Assuming I can show my friend the public key I received over the server, and she verifies it, then everything else can work as described right? As in, it wouldn't require anything as complex as the Signal protocol to send messages securely?
- Piskvorrr 9y agoWell, you'll need an independent channel to do this, which also needs to be resistant to MITM. (In-person works, even though it's bothersome - but you only need to establish this once) As long as it's a 1:1 chat, there's not much else to it - of course, great complexity comes to multi-user chats.