As mentioned in other comments, you have to trust Apple to hand you the correct public keys. They could easily MITM you and decrypt the messages on the server if they misrepresent the other party's public key. Additionally, the iMessages you send are signed by your private key, which is probably not something you want.
Apple Explains How Secure iMessage Is
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Re: Apple Explains How Secure iMessage Is
#12Author isn't very clever about crypto attacks. Sending device grabs all of the recipients public keys (as well as all of their own keys for other devices, which allows the conversation to be replicated on all of their own devices as well) hosted by Apple. Sending device has no way to verify those keys belong to the intended recipient . User has no way to verify which, or how many devices they are sending to. User doe…
Users get both a push notification and email when a new device is added to the key bag. So additionally this step would need to be maliciously skipped.
Re: Apple Explains How Secure iMessage Is
#13If all that is true, it sounds perfectly secure against anyone other than Apple and whatever law enforcement agencies they comply with requests from.
So, you know, really not secure at all.
Re: Apple Explains How Secure iMessage Is
#14The way Apple could "read" the messages is by sending a keybag down to the person sending the messages with another public key, one that Apple holds the private key for. For example if you have 3 devices (iPhone, iPad, MBP) and someone goes to send you a message, they have to re-encrypt the message three times because Apple would have sent them three public keys. Now if Apple were evil because of a government order,…
Lawful intercept isn't evil.
Re: Apple Explains How Secure iMessage Is
#15Unless Apple is omitting something or there’s some backdoor tucked into their many-layers-deep encryption (which, while unlikely, isn’t inconceivable) they really can’t read your iMessages without a fairly insane amount of effort. That is, assuming, that there isn't some code in the app that allows Apple to request that the app send your private key up to the server. It's conceivable that in order to comply with law…
> (which, while unlikely, isn’t inconceivable) Not only do I think it's not unlikely, I actually think it's pretty much a certainty that Apple has a backdoor in their code. After the slides detailing how easy it is for NSA to break into Apple phones I'd be simply shocked if they hadn't inserted such a vulnerability. Sounds to me like the author is applying a nice coat of white wash.
After reading a post by a Google engineer on this issue, I'm going to err on the side of believing that Google, Apple, and others aren't actually actively inserting back doors into their code.
https://plus.google.com/108799184931623330498/posts/SfYy8xbD...
Re: Apple Explains How Secure iMessage Is
#16Author isn't very clever about crypto attacks. Sending device grabs all of the recipients public keys (as well as all of their own keys for other devices, which allows the conversation to be replicated on all of their own devices as well) hosted by Apple. Sending device has no way to verify those keys belong to the intended recipient . User has no way to verify which, or how many devices they are sending to. User doe…
Users get both a push notification and email when a new device is added to the key bag. So additionally this step would need to be maliciously skipped.
And since Apple owns the infrastructure and we can't validate anything about it, there is little reason to believe they couldn't maliciously skip steps.
Re: Apple Explains How Secure iMessage Is
#17As mentioned in other comments, you have to trust Apple to hand you the correct public keys. They could easily MITM you and decrypt the messages on the server if they misrepresent the other party's public key. Additionally, the iMessages you send are signed by your private key, which is probably not something you want.
More to the point, they could be forced under court order (or FAA 702 order etc.) to MITM. This is a cousin to the Lavabit scenario.
Nothing wrong with end-to-end encryption, folks. Why don't we have more of it?
Re: Apple Explains How Secure iMessage Is
#18Earlier quoted context omitted.
Users get both a push notification and email when a new device is added to the key bag. So additionally this step would need to be maliciously skipped.
And since Apple owns the infrastructure and we can't validate anything about it, there is little reason to believe they couldn't maliciously skip steps.
Well you can kind of say that about the entire internet. Possibly "Evil" and/or compromised companies control everything, right?
Re: Apple Explains How Secure iMessage Is
#19The way Apple could "read" the messages is by sending a keybag down to the person sending the messages with another public key, one that Apple holds the private key for. For example if you have 3 devices (iPhone, iPad, MBP) and someone goes to send you a message, they have to re-encrypt the message three times because Apple would have sent them three public keys. Now if Apple were evil because of a government order,…
Lawful intercept isn't evil.
Are the NSA's intercepts lawful?
Re: Apple Explains How Secure iMessage Is
#20It is closed sourced anyway; so who knows if the document is correct, and who knows if there is a backdoor or a bug...