WhatsApp isn't installed by default AFAIK, but it is one of the first apps installed by millions, if not billions, on their phones.

In Korea, Taiwan and Japan, LINE became the de facto IM. In China, WeChat. But ain't sure if these are usually/always preinstalled in those markets.

Cheers.

In Korea I think the de facto IM is Kakao, LINE is only third (after FB messager) [0][1].

[0]: https://www.statista.com/statistics/898254/south-korea-most-...

[1]: https://www.quora.com/Which-is-the-most-popular-messaging-ap...

Thanks.

iMessage is end to end encrypted by default. Perhaps not as strongly, but it's a good default to begin with.

Key management is still centralized and controlled by Apple, so they can still MITM communications by messing with the key exchange.

iCloud backups (enabled by default) are not end-to-end encrypted.

So while it's technically E2E, in practice you get very little protection from it because it's broken by design.

I still use iMessage because of the user experience, but let's not be fooled by their misleading E2E claims; it's all just marketing BS.

If both parties disable iCloud on their phones, does Apple have any way to read messages sent via iMessage?

We have no idea and there’s no real way even in principle for us to know.

They can still pull off an MITM attack by sending the MITM’s keys (pretending to be the other user’s keys) because they control they key exchange.

It’s an active attack and can’t apply retroactively but within these constraints they can still do it.

Yes, if they add a wiretapping key to one or both of your key lists, which is silent/invisible to the sender.

Whenever key management is centralized, there is basically no security from the legal authority in the jurisdiction that the messaging vendor is located in. The vendor can always push you an MITM key. They can even show you the "correct" recipient key when you physically verify but use a different one for the actual message transfer and this would be a trivial easy to obfuscate switch in the program binary.

E2E with centralized key management is primarily to protect you from casual/private threats (vendor employees, snoopers in your or your recipients network) not from legal authority.

The Signal Foundation is based in Mountain View and both Moxie Marlinspike and Brian Acton are US nationals...

What’s stopping some US government agency from forcing them to insert code that causes the Signal app to a indicate it is behaving correctly but isn’t?

And don’t say “laws”.

If your threat model includes advanced persistent threats all bets are off.

Regardless of its security features it's Apple device only which is a deal breaker.