Is iMessage really an encrypted messaging app? (2021)

Yes, if your definition of "end-to-end encryption" means Apple can't read your messages (and I would argue that this is entirely reasonable), then the vast majority of messages sent through iMessage do not qualify. I would go so far as to say that it is false advertising to claim "iMessage is end-to-end encrypted" while Apple retains the ability to decrypt the vast majority of messages.

For what it's worth, Google's equivalent backup features do not have this loophole. Google cannot decrypt messages from your device backup without your device passcode, and while your device passcode is not a strong passphrase it is protected from brute force attacks by a hardware security module in the datacenter. I believe this is the same way Apple does it but only if you enable Advanced Data Protection.

This is probably useful for most non tech people, who might forget their passwords / lose keys, and don’t want to lose all access and all data.

If you’re tech savvy, you should probably enable ADP, I did it few months ago. When enabling it there’s multiple warnings about how you’ll end up completely locked out if you lose all your devices / lose recovery keys / lose all hardware authenticators. Iirc I was also forced to register at least 2 yubikeys.

( Copied parts of my comment in this thread https://news.ycombinator.com/item?id=41350989 )

I start with the assumption that anything sent through or stored by any provider can get decrypted and read. Then I don’t send or upload or backup anything I absolutely have to protect. The number of things in that category in my own life approaches zero, but other people may need more privacy. For them I would advise not using any messaging app or platform they don’t control.

It is generally the theme with most Apple apps. They all "protect your privacy" as long as you're ok Apple getting a copy in some way, unless you toggle something on or off. I believe Photos has a similar story.

What is your definition of "encrypted"?

And now there is contact key verification, which I believe requires iMessage on iCloud to be enabled

https://support.apple.com/en-us/118246

This seems to eliminate the problem listed in the article. However each person on each side of the conversation has to enable contact key verification with the other person manually and be on software above Sonoma or iOS 17.2. But then it (apparently) makes it so Apple can’t read your messages. I assume this is some kind of back door on apples part to counter an NSA initiative

Note that an intel iMac19,1 (only model) can upgrade to Sonoma without a T2 chip , so it could be possible to use such a machine to extract secret keys or at least hack or spoof contact key verification key (maybe only for the specific user though not a global key)