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Comment by pwg | Hacker News Reader

From the addition:

> (EXIF stripped via screenshotting)

Just a note, it is not necessary to "screenshot" to remove EXIF data. There are numerous tools that allow editing/removal of EXIF data (e.g., exiv2: https://exiv2.org/, exiftool: https://exiftool.org/, or even jpegtran with the "-copy none" option https://linux.die.net/man/1/jpegtran).

Using a screenshot to strip EXIF produces a reduced quality image (scaled to screen size, re-encoded from that reduced screen size). Just directly removing the EXIF data does not change the original camera captured pixels.

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I would like to point out that there is an interesting reason why people will go for the screenshot. They know it works. They do not have to worry about residual metadata still somehow being attached to a file. If you do not have complete confidence in the technical understanding of file metadata you can not be certain whatever tool you used worked.

True, but on Mac, a phone, and Windows I can take a screenshot and paste it into my destination app in a couple seconds with a few keystrokes. Thats why screenshotting is the go-to when you don’t mind cropping the target a little.

Little bit less convenient to use on a phone though - and I like that screenshotting should be a more obvious trick to people who don't have a deeper understanding of how EXIF metadata is stored in photo files.

Ffshare on Android is a one second step to remove exif data

With location services on, I would think that a screenshot on a phone would record the location of the phone during a screenshot.

It would be best to use a tool to strip exif.

I could also see a screenshot tool on an OS adding extra exif data, both from the original and additional, like the URL, OS and logged in user. Just like print to pdf does when you print, the author contains the logged in user, amongst other things.

It is fine for a test, but if someone is using it for opsec, it is lemon juice.

I built a tool for testing that a while ago - try opening a screenshot from an iPhone in it, you won't see any EXIF location data: https://tools.simonwillison.net/exif

Here's the output for the Buenos Aires screenshot image from my post: https://gist.github.com/simonw/1055f2198edd87de1b023bb09691e...

That is cool, but we cant be guaranteed that will always be the case, nor could we make a statement about all phones, it would be a phone by phone basis. Esp on Android where someone could have an alternative screenshot application.

Depending on your threat model, I'd argue that it would be impossible to prove that metadata is not included within the image itself (alpha channel, noise, pushed pixels, colorspace skew, etc).

I'd be interested in stego techniques that can survive image reduction and denoising.

Take a photo of the image displayed on your laptop screen with your phone. Ultimate EXIF removal!

Screen dust and smudges now form a fingerprint to cross correlate images.

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