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December 18, 2014

Smoke Signals, Morse Code or … ?

It seemed like a straightforward question. If you use Apple’s Contacts.app to store your contacts, you’ve surely noticed this behaviour: some of your contacts auto-magically sprout clickable links for Facetime video/audio chats, with no intervention on your part. I was curious enough to submit a query about it, via Apple’s Support Site:

Contacts.app seems to know whether each of my contacts has registered their email for FaceTime, even if I have NEVER tried to facetime with them (or call their cell-phone or …). How does it do this? Are all of the email addresses in my addressbook automatically uploaded to Apple’s servers? If so, how do I turn this off, as it seems to be a MASSIVE invasion of my privacy.

That was a month and a half ago (2014/11/02). Today, I received a response:

Dear Jacques,

Thank you for your recent email.

We sincerely understand your frustration and apologize for any inconvenience this has caused you. We understand you have questions and concerns about your contacts and FaceTime. Because of the nature and complexity of this issue, Apple does not offer this type of assistance or support through written correspondence.

For further assistance, please contact Apple Support. To locate your local Apple phone number, please visit:

support.apple.com/kb/HE57

Thank you, Apple Customer Care

Can it really be that the explanation is too complex for “written correspondence”? What other communication method would be more adequate?

Or maybe one of you know the answer. How does Contacts.app determine which of the email addresses in my addressbook have been registered for Facetime?

Posted by distler at December 18, 2014 3:14 PM

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14 Comments & 0 Trackbacks

Re: Smoke Signals, Morse Code or … ?

Most likely they put the email address through a one-way hash function and then ask the server if that hash is registered. So long as the request to the server doesn’t include your personally identifiable information there’s no leak of info here - you haven’t revealed your contacts email address or even that you have that ID as one of your contacts.

It’s quite a common practice these days.

Posted by: Adrian Sutton on December 18, 2014 5:59 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

So long as the request to the server doesn’t include your personally identifiable information …

That’s a dubious assumption, especially for the Contacts App on the iPhone. I’m more willing to believe that the requests from the Desktop MacOSX App are anonymized.

But, even if “your” personal information is suppressed, we have a situation here, where every Apple user is sending Apple a complete list of (the Facetime-registered subset of) his/her contacts. Dropping the user from that dataset is only a tiny omission.

…you haven’t revealed your contacts email address or even that you have that ID as one of your contacts

Sure you have.

If the Hash is registered, then they know who it’s registered to. And now they know that person is on your contact list.

At least, this way, they don’t learn the email addresses which are not registered for Facetime (those yield unknown Hashes).

Handing over (roughly) half of my contact list is better than handing over the whole list. But not by much.

Posted by: Jacques Distler on December 18, 2014 8:53 PM | Permalink | PGP Sig | Reply to this

Re: Smoke Signals, Morse Code or … ?

Apparently the FaceTime app on the Mac and the FaceTime settings on iOS devices lets you specify what contact methods (phone numbers, e-mail addresses) others can use to find you. I don’t know whether Apple is opting you in by default, but you can control it.

Posted by: Adam Rice on December 18, 2014 9:53 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

Just two questions:

Is FaceTime better (i.e. clearer, etc.) than Skype, Google, or other services?

Which tablet would you prefer? iPad or Android?

Posted by: Pete on December 19, 2014 12:51 AM | Permalink | Reply to this

Focus, please …

What do either of those have to do with whether my contact list is being sent (without my knowledge) to Apple?

This is a post about the behaviour of Contacts.app, not about Facetime.app.

Posted by: Jacques Distler on December 19, 2014 12:57 AM | Permalink | PGP Sig | Reply to this

Re: Focus, please …

Well, it’s off topic. I was just wondering what your opinion is. Is FaceTime better? Which tablet would you recommend? iPad? A particular Android tablet that has caught your eye?

Posted by: Pete on December 19, 2014 5:10 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

I know Apple automatically “assumes” someone’s number is registered for facetime or iMessage if you add their number with the iPhone label instead of regular old mobile, or work. As for emails, my guess is you have iCloud backup enabled for your contacts? Everyone’s information is uploaded by default!

Posted by: ThinkCode on February 19, 2015 7:28 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

I know Apple automatically “assumes” someone’s number is registered for facetime or iMessage if you add their number with the iPhone label instead of regular old mobile, or work.

That’s false.

As for emails, my guess is you have iCloud backup enabled for your contacts?

That would be stupid. If I wanted to share my contact list with Apple, then I would have turned on iCloud Backups. Since I don’t, I didn’t do that.

Posted by: Jacques Distler on February 20, 2015 12:39 AM | Permalink | PGP Sig | Reply to this

Re: Smoke Signals, Morse Code or … ?

Well I don’t even have a Mac so I can’t check this myself but have you considered using a network packet sniffer like wireshark to investigate what’s going on? You could run it in the background and then add some contacts and see what happens.

Posted by: jesus on February 20, 2015 8:54 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

Peter Woit is talking about you at his latest post:

http://www.math.columbia.edu/~woit/wordpress/?p=7705

Posted by: Dave on May 8, 2015 11:53 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

Seriously? Does anyone still care what Peter Woit has to say?

I stopped paying attention years ago.

Posted by: Jacques Distler on May 9, 2015 12:11 AM | Permalink | PGP Sig | Reply to this

Re: Smoke Signals, Morse Code or … ?

Apparently, your colleague, David Ben-Zvi still cares.

http://www.math.columbia.edu/~woit/wordpress/?p=7732#comments

Posted by: Stanley on May 20, 2015 5:06 PM | Permalink | Reply to this

Re: Smoke Signals, Morse Code or … ?

David desperately needs to start a blog of his own.

An excellent bit of explication of Geometric Langlands (and not the first such explication he has left in the comments section of some blog or other), but totally wasted over there.

Posted by: Jacques Distler on May 20, 2015 8:07 PM | Permalink | PGP Sig | Reply to this

Re: Smoke Signals, Morse Code or … ?

Have you looked at papers (such as this one, http://arxiv.org/pdf/0707.2283v1.pdf) that claim that conformal gravity doesn’t contain ghosts?

I’m surely no expert, but would love to know what (if any) flaws there are in this.

Apparently, ‘t Hooft won an essay competition with his essay on conformal gravity:
http://www.gravityresearchfoundation.org/pdf/awarded/2015/Hooft_2015.pdf

How does this evade “Georgi’s objection” you mentioned in a blog post from 10 years back?

Posted by: Stanley on May 20, 2015 11:57 PM | Permalink | Reply to this

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