If it's a mobile app, people are generally used to it using the mobile number. For the average nontechnical user it reduces barriers to entry as you don't have to create yet another account with username/password, and it can be used for address book import (which I agree isn't very private!)

See this article on this topic:

https://whispersystems.org/blog/contact-discovery/

Threema doesn't.

https://threema.ch/en/faq/identity_expl

My understanding of the perspective of the authorities on encryption in messaging is that it doesn't matter what you say, it matters who you say it to and when; additionally, it matters whether you're speaking cryptically or not.

Whatsapp requires a telephone number as it uses that for your ID. Same with RedPhone. TextSecure (android) can certainly be used without registering -you just miss out on the push-via-data service.

> Whatsapp requires a telephone number as it uses that for your ID.

I understand that. I'm questioning why they've set such an arbitrary restriction in the first place.

It's not arbitrary. It simplifies things for users a lot. No usernames or passwords to remember. Many telcos link your phone number to your identity which you cannot really lose, so therefore also no chance of losing your WhatsApp account. Also, more importantly, solves the contact discovery/social network problem by letting you reuse the phones address book.

You'll find that many people are very reluctant to give up that sort of information about themselves though, whether it be for privacy or because they don't like being incessantly spammed. I understand it existing as an option, maybe even a default, but to make it to the only method of authentication seems insane. Sure, many users will deem that the benefit of using the application overwhelms any negative implications, but it would be nicer if they weren't forced to make that tradeoff in the first place.

I'm not against the option existing, I'm against it being the only option.

>You'll find that many people are very reluctant to give up that sort of information about themselves though

Erm. I suspect you don't realise that WhatsApp has over half a billion users. It's as large as the major webmail services and nearly as large as Facebook itself. Society has reached consensus on this issue very fast - phone numbers as your identity work well, and any app that wants to be accepted by the market has to work this way exclusively.

> Erm. I suspect you don't realise that WhatsApp has over half a billion users.

I'm well aware.

Just because something has given up this information doesn't mean they approve of being asked, just that they evaluated that the positives outweigh the negatives. If I put out snail pellets to save my lettuces it doesn't mean I enjoy the death of any animal, it just means that I value the outcome of healthy lettuces more than living mollusks.

> any app that wants to be accepted by the market has to work this way exclusively

I see nothing that suggests this, outside of a successful app despite it. Maybe they'd have more users if they didn't have such an asinine policy. We don't (and probably can't) know for sure.

What percentage of potential WhatsApp users is "many"? I'd suggest it's more like a minimal amount, otherwise why do you think WhatsApp gave up greater market share?

If you want to talk to your friends/family, you have to give up who you are.

What's your solution here? How would I be able to talk to you?

Usernames just like every other service on the internet which doesn't use phone numbers or email addresses for authentication and identification.

As a person who doesn't even own a mobile phone at all I support you wholeheartedly. How am i supposed to use anonymous messenger giving him my real phone number!