Re: Secure Chats
Or just don't send messages that you haven't encrypted yourselves too.
If YOU encrypt the message properly, you could CC: in the head of GCHQ, let WhatsApp double-encrypt it, or give it away in packets of cornflakes, and it would make no difference.
What you can't hide - and what spooky agencies should be using - is the metadata. What account you spoke to. When. For how long. How large a message. Who else did that speak to? Can you tie that to another person? That's what'll convict you if you can't provide a reasonable defence, and that's what they'll use to trace the networks (whether or not they bother or can get anything useful, that's subjective).
But the actual ENCRYPTION of a message is something that is quite easy to do. Do it offline and you know your key isn't compromised and don't have to rely on WhatsApp to secure it for you.
One of the stated purposes of encryption is that you can broadcast the message over a non-secure channel. Beyond that, it really doesn't matter. There are no such things as known-plain-text attacks, etc. any more with modern encryption, even.
If you're worried about the guy at the other end being your intended target of the message, that's what keys are for (you would have to verify them by some other means - again, an entry point for a spy agency, but pretty much they can just print their public key on posters and put them up around London if they like, that's why it's CALLED a public key - it doesn't help at all in decrypting the message and only the PRIVATE KEY that generated it could do ever that).
But the medium of transport? You could put it on Twitter with all the permissions open. You'd be giving nothing away about the content of the message by doing so that you aren't giving away by every other possible means. But they still won't know WHAT was said.