WhatsApp Encryption Security Flaws Could Allow Snoops to Slide into Group Chats
Here&#x27;s how WhatsApp group messaging works: membership is maintained by the server. Clients of a group retrieve membership from the server, and clients encrypt all messages they send e2e to all group members.<p>If someone hacks the WhatsApp server, they can obviously alter the group membership. If they add themselves to the group:<p>1. The attacker will not see any past messages to the group; those were e2e encrypted with keys the attacker doesn&#x27;t have.<p>2. All group members will see that the attacker has joined. There is no way to suppress this message.<p>Given the alternatives, I think that&#x27;s a pretty reasonable design decision, and I think this headline pretty substantially mischaracterizes the situation. I think it would be better if the server didn&#x27;t have metadata visibility into group membership, but that&#x27;s a largely unsolved problem, and it&#x27;s unrelated to confidentiality of group messages.<p>In contrast, Telegram does <i>no encryption at all</i> for group messages, even though it advertises itself as an encrypted messenger, and even though Telegram users think that group chats are somehow secure. An attacker who compromises the Telegram server can, undetected, recover every message that was sent in the <i>past</i> and receive all messages transmitted in the <i>future</i> without anyone receiving any notification at all.<p>There&#x27;s no way to publish an academic paper about that, though, because there&#x27;s no &quot;attack&quot; to describe, because there&#x27;s no encryption to begin with. Without a paper there will be no talks at conferences, which means there will be no inflammatory headlines like this one.<p>To me, this article reads as a better example of the problems with the security industry and the way security research is done today, because I think the lesson to anyone watching is clear: don&#x27;t build security into your products, because that makes you a target for researchers, even if you make the right decisions, and regardless of whether their research is practically important or not. It&#x27;s much more effective to be Telegram: just leave cryptography out of everything, except for your marketing.