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File: 1487065768448.png (17.49 KB, 225x300, metadata-kills.png)

No.4140

So, dear Lainons I want to "sign" an image with some text, not a watermark but embed my signature within the image. Maybe there will be some negligible quality loss but I'd like it to be readable by the some app.

I suppose it's similar to how layer works but would run as a stand alone application (for large image files). It doesn't use meta-data tags like EXIF or anything similar, the message would be encoded into the file. If it gets cropped, re-encoded or modified in any way, then the signature is destroyed (therefore the file is no longer authentic).

Does such a program or suite of programs exist? I know a simple screenshot will copy any image but this is more as a means to preserve the source for those interested in knowing.

  No.4142

>>4140
@image
It is a scientifically proven fact that life is a sexually transmitted disease that leads to certain death. Everything else that seemingly leads to death are in fact side effects of life.

  No.4147

>>4140
Does your signature have to be an actual signature, or could it just be an encoded row of dots and dashes or something similar? I'm thinking you could encode your text into dots using a cipher and embed those pixels in the very top row of pixels of your image. It wouldn't be too difficult to specify the location of those pixels but color would be trickier - say your image is mostly black, you wouldn't want to use black pixels to encode your signature, etc.

  No.4153

File: 1487120644789.png (493.85 KB, 200x174, new.png)

What if you added a zip file containing whatever data you want. Pic related as an example.

I created this image by first zipping up a file, then I concatenated the file and an image
cat image.png zip > new.png
You can access the data by simply
unzip new.png

I quickly tested converting the image to another format using imagemagick and could not receive the data. This should also occur when the image is modified in other ways.

  No.4160

steganography hides data in the least significant bit of the unencoded image data. Its not visible in the resultant image. There are programs that do this like jphide.

  No.4202

>>4147
It could be anything really but the signature can be deconstructed into a binary representation. This is kind of neat in that it can survive a crop or certain encodings if the message is more important than the image. However, it's the other way around for my use case. Sounds abstract but I'm looking for ways to ghost-sign original images.

>>4153
Hmm, this actually worked! Really simple use of common utilities and provides a nice container for anything. Thank you this is pretty useful for hiding easter eggs (or an encrypted mess for that matter). Opens up possibilities with other image formats that rely on different compression algorithms.

>>4160
I've seen a similar program but I end up with noticeable artifacts all over the image. Last one I tried (can't recall the name) even had some kind of verification to prevent forgery but degraded the image to the point where it was unusable. However, it was pretty good at hiding the payload in innocuous image formats intended for the web.

Thanks for the suggestions my dear Lainons!

  No.4451

>>4202
>but degraded the image to the point where it was unusable
I think if you were only dropping in a small amount of data on a large file this would become negligible. Make your jpgs 5MB or so?

>>4160
Errm, Just asking... Could anyone get me started on how to compile this? What compiler is this for? is there any good links that can hold your hand through the process of doing your first compile? - can you cross compile for Win and Linux?

  No.4769


  No.4775

>>4451
>.c

Looks like it's linux only;

download it and then cd to the directory and type:


  make
sudo make install

  No.4943

man steghide
This is the tool I typically use for sending small files on imageboards.