Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Privacy: Is That iPhone?

foundation.mozilla.org

Post reply on HN
Print view View original

71–80 of 188 posts

Re: Privacy: Is That iPhone?

#71

Post by gorgoiler »

gruez wrote: post #57
gorgoiler wrote: post #19

Earlier quoted context omitted.

I applied filters and took a screenshot of the screenshot to reduce image fidelity in case it contained any [covertly embedded]* identifying information [in the form of watermarks or hidden pixels] . *added for clarity.

I'm sorry, but that's some tin foil hat level paranoia with no basis in reality. What's your threat model here? That Apple wants to deanonymize HN posters by tying them to their screenshots? Considering that they own the operating system, they could skip all the complicated and detectable stenography-in-screenshots and smuggle your mobilesafari (or webkit, which all apps are forced to use) browsing history and cookie…

That’s fine, it’s not a big deal, though I was specifically asked.

The main thing I would worry about is actually not Apple; instead (1) what information might Apple hide in plaintext in the image that a third party could extract?; and (2) what identifiers might there be that a third party could use to correlate multiple images as being from gorgoiler’s phone?

But honestly it just feels odd to upload a screenshot without doing something to scrub it. I find it helpful to practice good security even when, as you point out, the probability of it being necessary is very low.

Re: Privacy: Is That iPhone?

#72

Post by baroffoos »

fpgaminer wrote: post #36
gorgoiler wrote: post #19

Earlier quoted context omitted.

I applied filters and took a screenshot of the screenshot to reduce image fidelity in case it contained any [covertly embedded]* identifying information [in the form of watermarks or hidden pixels] . *added for clarity.

In case people aren't aware, such a thing _is_ possible. Companies have used steganography techniques in the past to secretly embed identifiers into movies and other visual content. It's been used to track down the movie leakers, for example. Another example; most printers covertly embed an identifier in their prints. I have a vague memory of a pre-release video game doing it? Or maybe it was just debugging informati…

Microsoft embedded an ID in one of the animations on the xbox 360 dashboard which could identify the person who leaked video of a beta game.

Re: Privacy: Is That iPhone?

#73

Post by hardwaresofton »

If only someone had created a viable alternative to both Google and Apple's phones. Maybe they could base it on the browser? Web technologies are getting pretty good these days. One of the popular browsers that are an alternative to safari and google chrome... Like some sort of browser-OS.

Re: Privacy: Is That iPhone?

#74

Post by desyerious »

retpirato wrote: post #9

The problem is that Apple has always claimed ios provides more privacy (& security) than android, but that's irrelevant if you don't make sure your users are capable of finding the settings. Apple has always marketed to people who are (at least perceived to be) largely tech illiterate (while claiming you have to be extremely tech savvy to use android which is a lie), so if they view their users that way they should m…

There’s also the difference between privacy and anonymity.

Apple has tools in place for privacy, but none for anonymity. For example, requiring a full name and physical address to sign up for the App Store (Microsoft, despite all it’s telemetry, let’s you install apps from their store without an account).

I’ve heard suggestions to give Apple a fake name/address, but what if they start verifying like Facebook by requiring government issued ID?

Worst is new iCloud accounts now require a phone number for verification.

Re: Privacy: Is That iPhone?

#75

Post by zigzaggy »

oil25 wrote: post #34

Anyone disillusioned by the thought that Apple values privacy would be well served by reading iOS, The Future Of macOS, Freedom, Security And Privacy In An Increasingly Hostile Global Environment - https://gist.github.com/iosecure/357e724811fe04167332ef54e73... There is so much more to privacy than is made apparent to the user as a few OS knobs to "limit" ad tracking.

Thank you for sharing this very helpful / valuable information. I’m always looking to go deeper down the rabbit hole of security.

Re: Privacy: Is That iPhone?

#76

Post by gruez »

gorgoiler wrote: post #71
gruez wrote: post #57

Earlier quoted context omitted.

I'm sorry, but that's some tin foil hat level paranoia with no basis in reality. What's your threat model here? That Apple wants to deanonymize HN posters by tying them to their screenshots? Considering that they own the operating system, they could skip all the complicated and detectable stenography-in-screenshots and smuggle your mobilesafari (or webkit, which all apps are forced to use) browsing history and cookie…

That’s fine, it’s not a big deal, though I was specifically asked. The main thing I would worry about is actually not Apple; instead (1) what information might Apple hide in plaintext in the image that a third party could extract?; and (2) what identifiers might there be that a third party could use to correlate multiple images as being from gorgoiler’s phone? But honestly it just feels odd to upload a screenshot wit…

>The main thing I would worry about is actually not Apple; instead (1) what information might Apple hide in plaintext in the image that a third party could extract?; and (2) what identifiers might there be that a third party could use to correlate multiple images as from gorgoiler?

A lot, actually. But why Apple would take the engineering resources to implement this, and risk all the reputation damage? If they're doing it for the money, how would they monetize it? If they're being coerced by the government, what's the government's motivations? In both cases, is smuggling bits in screenshots really the most plausible way to do it? Surely there must be some better way stenography in screenshots?

>But honestly it just feels odd to upload a screenshot without doing something to scrub it. I find it helpful to practice good security even when, as you point out, the probability of it being necessary is very low.

On the flip side, if you do unusual obfuscation of your uploaded image (eg. heavy post processing), that in itself is an identifying characteristic. You're going to be that guy who uploads his screenshots in greyscale, with heavy compression and blurring. https://xkcd.com/1105/

Re: Privacy: Is That iPhone?

#77

Post by kevin_thibedeau »

api wrote: post #53
mojuba wrote: post #48

Earlier quoted context omitted.

Unfortunately the majority of more or less useful or popular apps are also linked against various analytics/attribution platforms, often many of them at once. Mixpanel, Amplitude, AppsFlyer, Branch to name a few, plus Facebook and/or Google. In fact having any of the Google's or Facebook's SDKs means tracking, e.g. Maps, Login etc. Somehow these platforms have no problem with identifying users across their client app…

Mobile is all about surveillance as near as I can see. The whole purpose of it is to track users.

How else should a telescreen function?

Re: Privacy: Is That iPhone?

#78

Post by thenewnewguy »

mobjack wrote: post #66
varenc wrote: post #40

Mozilla suggests resetting the IDFA once per month...but that seems pretty trivial to workaround? If an app you used previously starts up and sees that your IDFA changed, it's easy for that app to know that the old IDFA and the new IDFA refer to the same user! This tracking is all possible because iOS gives every app on the device the same IDFA (advertising identifier [1]). They can then correlate all your activity a…

You don't need an IDFA to track someone in the same app. You can generate your own UUID to use. The value of the IDFA comes from coordinating user behavior across apps. Targeting ads is one use case, but it is also used in conversion tracking, which is very valuable to advertisers. They can know if ads in one app resulted in people buying things in another app. Edit: fixed typo

The point is that the app can just record the old IDFA, and when the IDFA changes whoever is doing the comparison between two apps knows that the old and new IDFA are one and the same.

Re: Privacy: Is That iPhone?

#79

Post by gruez »

gorgoiler wrote: post #39
austinjp wrote: post #32

Earlier quoted context omitted.

Genuine question: what is a tracking watermark, in the context you're discussing?

Imagine that whenever you took a screenshot the text “TAKEN ON AUSTINJP’S IPHONE” were written across the page. A “watermark” is simply a version of that designed to be invisible or imperceptible to the human eye, for example by embedding information in the least significant bits of the pixel colors. “Digital Watermark Steganography” is a good search term for further investigation. As is the case with many security t…

>A “watermark” is simply a version of that designed to be invisible or imperceptible to the human eye, for example by embedding information in the least significant bits of the pixel colors.

In this case however, it's hard to imagine how you'd do this without being detected. If you loaded the screenshot into mspaint and used the paint bucket tool, any color differences will become apparent. You could limit your modification to the edges, but detail there is going to get wiped by jpeg compression (if any).

Re: Privacy: Is That iPhone?

#80

Post by jessaustin »

mobjack wrote: post #66
varenc wrote: post #40

Mozilla suggests resetting the IDFA once per month...but that seems pretty trivial to workaround? If an app you used previously starts up and sees that your IDFA changed, it's easy for that app to know that the old IDFA and the new IDFA refer to the same user! This tracking is all possible because iOS gives every app on the device the same IDFA (advertising identifier [1]). They can then correlate all your activity a…

You don't need an IDFA to track someone in the same app. You can generate your own UUID to use. The value of the IDFA comes from coordinating user behavior across apps. Targeting ads is one use case, but it is also used in conversion tracking, which is very valuable to advertisers. They can know if ads in one app resulted in people buying things in another app. Edit: fixed typo

How many users would care about this distinction you're attempting to draw between "targeting ads" and "conversion tracking"?
Post reply on HN