You want to send or post a photo, but don’t want to show the whole image. Maybe it’s a screenshot and you do not want to tell the world about your mobile provider and other personal visible details on a screenshot, or you may want to blur your background to hide your location, or or or…

Did you know that it is easy to reverse engineer cropped, blurred or manipulated photos back to their original state, thereby revealing what you wanted to hide by manipulating the photo in the first place? It is called an “exploit” (as in exploiting a loophole or weakness in a programme or app). Recently, such a weakness has been found in the built-in cropping feature on Google Pixel phones, but the weakness is also present in iPhones and other Android phones (read this Wired article to know more).

While companies can patch the exploits, all redacted photos already online (and if you use a cloud service, your photos are most likely already online) are vulnerable to it. When you crop a photo, what happens is the process tells the file to pretend that the cropped out section is not there, but it actually is still there.

As we all now know (and if you don’t, you should), if there is anything you do not want to make public, do not post it online. It is safe to consider that anything you have posted online is now in one way or another known to someone. And deleting what you have already posted does not help. You are just removing it from your view. Your photos are probably already in multiple datasets.

One way to really crop photos is to use… SIGNAL! Yes. You may know Signal as one of the most secure and private messaging platform, but it is also a great tool to REALLY crop out stuff from your photos so they can’t be reversed engineered. How to do that? Open Signal, take a photo, open the editing tool, crop, change as needed and save. Then send to “Note To Self” (another great feature of Signal for storing info).

If you have not downloaded Signal yet, you can find it in your app store, or here.