8/14/2023 0 Comments Redacted text twitterA black bar in different positions is "redacted" using a mosaic pattern. The following animations illustrate this idea. Therefore, by observing the color difference of the bigger squares in between frames, and correlating it with the movement, it should be possible to extract additional information and create an output image with a higher resolution. Reversing pixelation in videos without guessingĪfter seeing many videos where information has been blurred using the Mosaic method, I wanted to implement an idea that came to my mind: Since the camera is often moving relative to the blurred object, the boundaries for the bigger squares are also often moving relative to the real world. Javplayer automatically detects blurred regions and performs upscaling via TecoGAN, and another person spent months improving their custom GAN that was trained with leaked videos (search for "De-Mosaic JAV with AI, Deep Learning and Adversarial Networks"). Side note: The potentially most extensive research on the problem of programmatically unblurring mosaic'ed regions from videos was done by Japanese Adult Video enthusiasts. The current state-of-the art algorithms use some form of machine learning such as a Convolutional Neural Networks ( VESPCN) or Generative Adversarial Networks ( TecoGAN). Since a pixelated video can also be interpreted as low-resolution, using video upscaling techniques could be a viable approach. In case all frames are correctly blurred, a different approach is required. While this is usually desirable to reduce the spread of this information, it also makes it possible for a malicious actor to detect them easily and in an automated fashion by immediately downloading new uploads from documentary/news channels and diffing them with a download from a later date. In some of the observed cases, the mishaps were fixed after being noticed (e.g. Multiple camera shots, each leaking different information that can be combined (see the BTC QR code story).Missing blur in the first/last frame after/before a cut. Unblurred reporter's email address which could also be used to retrieve the previously blurred result page (and cyber bully her?) (the black box was added by me) Gaussian blur (or similar): Using a specific kernel, the new color of every pixel is influenced by its surrounding pixels (via a weighted average).Mosaic/Pixelization/Box Linear Filter: Multiple pixels are merged to a bigger one with the color being the average of the original pixel values.Instead of removing all information for a particular region, here the information density is only reduced.īlurring is usually achieved using one of the following two methods: This technique however does not work for simple image formats that only store one layer of pixel information (except for surprising edge cases when using transparency).Ī popular alternative to redacting information with a colored box is blurring. As text and objects/images in those files are stored as different objects in "separate layers", redacted text can sometimes still simply be copied, and colored boxes that were intended to hide information can often be removed to reveal the redacted content. One of the best known attacks on digital redaction methods works only on specific file formats, e.g. In this blog post, I'll discuss image/video blurring methods and their weaknesses and present a simple yet effective method to get a high-resolution image from a pixelated video in order to recover redacted information (with no guessing involved). It's therefore no wonder that some people might have a motivation to try to reverse such a redaction for various reasons. Information that has been redacted is often the most interesting.
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