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I'm confused what does the client have to do with this. My understanding of these end to end encryption models is with public/private keys. You (Facebook, Whats

by kovek 8y ago

I'm confused what does the client have to do with this. My understanding of these end to end encryption models is with public/private keys. You (Facebook, Whatsapp, or the user) generate a private and a matching public key. You distribute the pair of keys to the user who'd like to do communication. The user should not share their private key, not even to Facebook or Whatsapp. The user publishes his public key so other can encrypt messages using the user's public key and send their messages to said user. The user then uses the private key to decrypt the encrypted message. If Facebook keeps a copy of the private key, then they could read the encdypted message. Maybe the client itself is generating the keypair. In this case, the only issue I can see is the following: when the user wants to communicate with a friend, how can they be sure that the profile they are sending messages to (as displayed by their user interface and communicated by Facebook or Whatsapp or the friend's server) actually do belong to their friend? I'm confused what you were talkimg about, with the client build possibly being a trojan

indigo945 8y ago
>Maybe the client itself is generating the keypair. In this case, the only issue I can see is the following: when the user wants to communicate with a friend, how can they be sure that the profile they are sending messages to (as displayed by their user interface and communicated by Facebook or Whatsapp or the friend's server) actually do belong to their friend? That's exactly the point though, how can they be sure in the event that their client (on the author's side) is a trojan? If the "author" client is deliberately compromised, there is no longer any reasonable means of ensuring that the public key the author uses to encrypt the messages is actually equal to the public key the recipient published. Of course, this point is very much riddled with paranoia: it is exceedingly unlikely that the WhatsApp client deliberately contains such a trojan, especially since there are much easier ways of gaining access to user's messages (such as compromising their firmware with some form of rootkit, possibly installed via the baseband, and then simply sending copies of the local message cache to the NSA).
nnd 8y ago
The only way to know for sure is to verify your friend's signature in offline.

by kovek 8y ago

indigo945 8y ago

>Maybe the client itself is generating the keypair. In this case, the only issue I can see is the following: when the user wants to communicate with a friend, how can they be sure that the profile they are sending messages to (as displayed by their user interface and communicated by Facebook or Whatsapp or the friend's server) actually do belong to their friend? That's exactly the point though, how can they be sure in the event that their client (on the author's side) is a trojan? If the "author" client is deliberately compromised, there is no longer any reasonable means of ensuring that the public key the author uses to encrypt the messages is actually equal to the public key the recipient published. Of course, this point is very much riddled with paranoia: it is exceedingly unlikely that the WhatsApp client deliberately contains such a trojan, especially since there are much easier ways of gaining access to user's messages (such as compromising their firmware with some form of rootkit, possibly installed via the baseband, and then simply sending copies of the local message cache to the NSA).

nnd 8y ago

The only way to know for sure is to verify your friend's signature in offline.