This app covers all the bases in terms of protecting personal information and guarding against hackers, but all of that privacy can make it hard to see what your kids are doing. Threema's first good move is creating randomly generated IDs for each registered user. Adding personal information (phone number, email, profile picture) is entirely optional here; if you want, you can be 100% identified by your Threema ID, your public key (QR code), and the nickname of your choice. This is great, because there's nothing for Threema to pass along to third parties. Your friends can find you by any of these forms of ID, and you can ensure your messages really come from you by using the free Threema QR code plug-in (a separate download) to scan your key. You can even protect your conversations by assigning PINs to chat sessions.
Of course, as good as this level of security might be, it could be worrisome for parents, since tech-savvy kids and teens could use the app to easily hide their activities from parents and other authority figures. Users can permanently delete chat sessions, and content is deleted from the servers upon delivery, so the developer can't even provide information to law enforcement. In addition to that, kids can send files, photos, and videos that can be deleted with chat sessions, make encrypted phone calls, and use the app to send their locations via text. Because of all this, Threema's security features are a double-edged sword: On one hand, its sensible, ad-free (and spyware-free) interface makes it a breeze to use, and it's comforting to know hackers aren't listening in every time you send a text or make a call. On the other, knowing your kids could use the app to hide what they're up to is highly unsettling. In the end, it's a great way to protect kids and teens, but whether you let them use it depends on how openly your family communicates.