[ Article in Dutch can be found on the UGent news website. ]

Recently, the Belgian telecom provider Telenet presented the .comdom app, in collaboration with Child Focus. The .comdom app claims to enable safer sexting. It does so by adding a visible watermark containing the receiver’s name and phone number. The watermark is visible in the entire picture and is not easy to remove with common image editing tools such as Photoshop, at least not without making the entire picture unrecognizable, so Telenet says. As such, the watermark is an incentive against leaking the private picture, since everybody would know who leaked it. But will it withstand modern AI technology?

Watermarked image, using the .comdom app

The .comdom app, supported by well-known and trusted organisations, claims to be more secure than apps such as Snapchat and Confide which only give an illusion of online security. However, we were suspicious of this bold claim, and therefore investigated the app closely. In a few days, we developed a tool that automatically removes a watermark while retaining a relatively-high image quality. In this way, it enables receivers to leak the private pictures without being identifiable.

Artificial intelligence can remove the watermarks

We broke the .comdom watermarks by training a simple convolutional neural network on thousands of random pictures with and without watermarks. To produce this training data, the watermarks were randomly generated in the same way the app does. As it turns out, Telenet has underestimated the power of modern AI technology.

As a note: We will not publish our software to remove the watermarks, in order to protect the people who have used this app, believing it would protect their photo. Of course, anyone with the skill can recreate similar software. Therefore we advise everyone to be cautious with respect to this app.

Unwatermarked image, using our watermark removal tool

Not all is lost: the good

Truth be told, there are also positive aspects about the app. First, it reminds the user to make themselves unrecognizable, and has a built-in function to blur their face (even though faces are not always correctly detected). Moreover, the app helps to break the taboo of sexting. However, we regret that the app promises extra security by using the visible watermarks – which is a promise that they cannot keep. We argue that it is better to make people aware of the danger and limitations of online security.