WhatsApp uses the Signal Protocol, I'm not familiar with the details, but this post by OWS should[1].

[1] https://whispersystems.org/blog/whatsapp-complete/

>Even though we are the creators of the encryption protocol supposedly "backdoored" by WhatsApp, we were not asked for comment.

It's only a small step from criticism of WhatsApp crypto to criticism of Signal crypto. Why wouldn't moxie be interested?

because here it clearly says that signal had dealt with this problem https://tobi.rocks/2016/04/whats-app-retransmission-vulnerab... So it is solely whatsapp's fault

Especially when signal's interface has similar, if less severe, weaknesses.

He consulted on and helped them implement their E2E encryption.