Same way as in email, banking etc?
Also I find it puzzling that so many people here keeps on recommending WhatsApp over Telegram after all the lies from WhatsApps owner.
Edit: While I have no way to verify this, AFAIK both Telegram and Gmail stores data and keys in ways that makes them hard to access by everyone except for the user.
Telegram in particular say they do this by storing data and keys in different datacenters in different jurisdictions.
Add to this that WhatsApp has had their fair share of issues as well before they started working with Moxie.