JPEG compression protection

Many photo hosting sites and web proxies pinch JPEG files to speed up download. In this regard, specialists from Cambridge had the idea to adapt the well-known algorithm of Tovalds on copy protection of notes to JPEG-images. They developed a grid that generates moire for re-compression (a demonstration using the example of Google WAP proxy).

Original image	After recompression

If you are behind a firewall with recompression, then VOID will be displayed on both images.

For more on the algorithm, see Towards copy-evident JPEG images published in Lecture Notes in Informatics.

Such grids for moire generation are often used to protect various financial documents, including banknotes, tickets and checks. The idea is that when scanning or copying artifacts appear or obvious distortion of the grid.

Original image
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Photocopy



In this paper, the algorithm is adapted specifically to the JPEG algorithm so that the distortions introduced by the algorithm manifest themselves to the maximum and display an inscription that is not visible on the original image.

Now researchers are working to adapt the system for video streams in which compression algorithms behave less predictably. Then it can be used to protect the original content from illegal copying.