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Article:
  Hiding Secrets with Steganography
Subject:   What happens if the image gets edited?
Date:   2003-12-08 11:39:27
From:   anonymous2
I'm curious to know what happens to the hidden message if the image is manipulated in some way by Photoshop or some other image editing application after the 'secret' message has been embedded, be it resized, cropped, rotated, etc. Is the 'secret' still extractable? What about after extreme editing that causes significant changes in file size. If I understand the concept correctly, the photo editing application should read the file comments when the image is loaded and then re-write them (unchanged) after the image is altered. However, since the 'secret' is encrypted it should make it impossible for the image editing software to even recognize and read the embedded comment in the first place. However, if it can, in fact, recognize even the encrypted comment, it seems we have accomplished little more then encrypting text. So then I must ask why even bother hiding the encrypted text? Why not just use PGP?


Scott N
maquis@purdue.edu

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Showing messages 1 through 4 of 4.

  • What happens if the image gets edited?
    2003-12-08 19:40:27  anonymous2 [View]

    In steganography a well written algorithm only takes care that the information is preserved only while compressing an image and any other operation we can be sure that the message is lost.
    Also the algo saves for compression because usually the data is stored in a bmp file and then compressed to a jpeg.
  • What happens if the image gets edited?
    2003-12-08 16:08:58  anonymous2 [View]

    I'm not sure why the author included the information about jpeg comments, as these program encode the hidden file in the jpeg itself (by flipping insignificant bits), not the comment. Editing them in anyform will surely render the embedded file unretrievable or atleast significantly corrupted.
  • What happens if the image gets edited?
    2003-12-08 14:28:45  anonymous2 [View]

    Editors can not recognize the encrypted comment.
    Editing can destroy the information.

    Why do this instead of PGP? PGP can be broken with enough computer power. The advantage of this technique is that they do not even know their is a code to break. Therefore, even 20 years from now, people may not be able to retreive the secret information, not because their computers are not powerfull enough to break your encryption, but because they do not realize the information is there to find.

    You could get a slighlty less effective but similar result simply by renaming your secret information something like "image.retrieval.dll" and hoping that no one bothers to try and decrypt it. But by puting it into a regular file, people are less likely to try and break the code.
    • What happens if the image gets edited?
      2003-12-09 04:46:53  anonymous2 [View]

      But people will know there is information to find. If you insert an encrypted message into a photo, it is fairly easy to
      figure out that white noise(the encrypted message) has been added "unexpectedly" at some point -- and without a lot of computer power.