Let's talk about iMessage again | Hacker News Reader

Let's talk about iMessage again

blog.cryptographyengineering.com

99 pointswglb29 comments

From the comments:

> Apple controls iPhones. They have root access, you don't. It's the future that Richard Stallman predicted in The Right To Read, except he thought it would be Microsoft. In this kind of situation, why would you even mention key substitution attacks? It's like speculating about the owners of an Internet café implementing a TLS MITM attack in their own network's router in order to spy on HTTPS connections originating from their own machines. Why bother when you're root?

Google, too, actually and it has even acted on it in the past to remove some apps/malware. Same for Microsoft remotely uninstalling Tor from Windows machines.

What is the source for "Microsoft remotely uninstalling Tor from Windows machines"? Is this regarding: Microsoft Malware Protection Center removing the Sefnit malware

Microsoft does not give a shit about Tor. There are, however, botnets that install Tor, and anti-malware software that will try to remove those botnets.

From the article:

> While it seems pretty obvious that Apple could in theory substitute keys and thus enable eavesdropping, in practice it may require substantial changes to Apple's code.

> Any way you slice it, it's a risky operation.

This is really really poor. A government is not going to give anything about that it might be risky. That's for Apply to handle. Further, the author of the article pretends that the key server is a black box that's not entirely understood and therefore it is safe because it won't be changed. Strange assumptions based upon guesses.

There's various ways to make it possible to comply with a government request. Just send a modified version of the software to the device, change the keyserver, etc. Anyway, the government is not going to care much about how you do it.

As a company you get some leeway with following rules but eventually there will be a fine big enough to make you comply. That's just what I noticed from customs across various countries.

> There's various ways to make it possible to comply with a government request.

The much more interesting question: how many ways are there to make sure, in advance, that you are unable to do so?

>> Apple controls iPhones. They have root access, you don't.

>> It's like speculating about the owners of an Internet café implementing a TLS MITM attack in their own network's router

This is also just another speculation. We can't know because it's closed source.

It's just a comment quote.

BUT what closed source project doesn't have Root?

Sure you can have encryption on client side BUT once again they have root to the encryption even.

So not really speculation as much as philosophy

It's a good point, but Macs also are iMessage clients and are arguably less locked-down than iPhones. (I could be wrong, but not sure you can say Apple has root on Macs the way they do on iPhones.) It would be suspicious to the intended recipient if a forged message appeared one way on an iPhone, but differently on a Mac (or didn't show at all).

I am not sure about this type of security argument generally. It says, with all the guns out there who cares about knives? Well, maybe lots of people still care about them. And they still hurt when you find yourself on the wrong end of one.

> Another perspective on iMessage -- one I've heard from some attorney friends -- is that key server tampering sounds like a pretty good compromise solution to the problem of creating a 'secure golden key' (AKA giving governments access to plaintext).... I see two problems with this view. First, tampering with the key server fundamentally betrays user trust, and undermines most of the guarantees offered by iMessage.

That horse has left the barn already. Services like OnStar have been repeatedly used and abused by law enforcement; once the service is created, the government gets a warrant (sometimes?) and undermines the service without any regard for the trust in company providing the service. We are not likely to be able to change that reality without a serious overhaul/oversight of the government's warrant scope and process.

There is ALWAYS a weak link. It’s a part of the problem. It’s built in. you make choices about trust and you either stick with them or you don’t. If you change, you change and it's no skin off of anyone's back.

Apple has spent ages building the trust of their users. It is not in Apple's _business interest_ to lie, cheat and steal their users' data.

There are some problems that can't magically be optimized away by computers right now...humans are humans after all. If it comes out that something untoward has occurred, then we deal with that bridge when we cross it. Until then, just keep them honest and roll on messaging as you feel comfortable...or don't, it's your decision.

My understanding is that the notification on phones when a new key is added is built into the OS and can't be easily bypassed. That notification shows up when the key is added. If the key isn't added on the device then messages won't be signed for it.

Also, I thought the consensus was that Apple was 'backdooring' iMessage by giving LE access to iCloud backups which include iMessage, not compromising iMessage directly?

> Also, I thought the consensus was that Apple was 'backdooring' iMessage by giving LE access to iCloud backups which include iMessage, not compromising iMessage directly?

Can you please expand on this? How would access to iCloud backup not compromise iMessage?

The backups store messages as plaintext within the [encrypted?] backup. This compromises the messages themselves, but not the iMessage protocol nor systems.

iCloud backups are not encrypted, and they include iMessage conversations. So the backups don't compromise the iMessage "service" or "application," but simply provide access to messages sent and received before the backup was made.

>Also, I thought the consensus was that Apple was 'backdooring' iMessage by giving LE access to iCloud backups which include iMessage, not compromising iMessage directly?

Consensus? First I've heard of this being a consensus. I've heard people say if Apple is backdooring, this is the way they'd do it, but no consensus on this actually happening. Care to go into this a bit more?

Consensus may have been the wrong word to use, but I've heard the same as you, that backups are a weak point in iMessage security, and a very plausible way for LE to get access.

is it required to have an iCloud backup when using iOS? Or is it something that can be opted out of? I'm just curious.

You can opt out, but I think it will be the default.

Not required. You can choose between iCloud backup, iTunes backup (even encrypt if you want) and no backup at all. iCloud is the most convenient though

Just have more than 5 GB of data and you can't backup to iCloud without paying monthly.

Photos are not included, Apps aren't (only their data), I'm not sure about music. It's gonna be hard to exceed the 5GB this way

Photos may be included.

"Here’s what iCloud backs up: Photos and videos on your iOS devices, unless you turn on iCloud Photo Library on your iOS device (iOS 8.1 or later)."

https://support.apple.com/kb/PH12519?locale=en_US

The photos hit the same 5 GB limit, so it's not like excluding or including them really changes anything. Photos are the #1 reason people hit the backup limit.

Thanks, didn't know that (I use iCloud Photo Library), but IIRC you can disable stuff from backing up, even photos

I currently use 18 GB with only a single iPhone. 14.6 GB of this is my iCloud Photo Library.

I've upgraded to iOS 9 GM and El Capitan GM, and I saw some new items show up in my iCloud Keychain, titled:

    PCS Backup
    PCS CloudKit
    PCS Escrow
    PCS FDE
    PCS iCloudDrive
    PCS iMessage
    PCS Maildrop
    PCS MasterKey
    PCS News
    PCS Notes
    PCS Photos

(They also have what looks like a base64 string in there, but I'm excluding that just in case it might be secret)

Just a guess, but between this and the fact that iCloud Backups were broken during the iOS 9 beta period, it seems like they might be encrypting backups now, as well.

The problem with encrypting backups is what do they use as the encryption key? You have to have some route back to the users password, as that's what they'll be using to restore. That leaves it vulnerable to a LE password reset even if the backup is encrypted.

iCloud Keychain solves this problem, if you use a complex passphrase:

http://www.slideshare.net/alexeytroshichev/icloud-keychain-3...

The key could be added to the appleid on the server, without telling the phone about it. Others sending messages to you would then also encrypt with the new backdoor key. Likewise, you don't get notifications about your friends' keys updating (in fact there's not even any UI to show the current keys for a contact), so your phone would start encrypting messages to the recipient's additional backdoored key silently too. :(

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